If you're a Samsung Galaxy S2 owner then you may have already received an update for your handset, which brings it bang up to date with Android 4.0 -- also known as Ice Cream Sandwich (ICS). If you feel that ICS doesn't offer enough to excite you, you could try one of the raft of custom ROMs available for the S2 instead.
The latest iteration of Google's all-singing, all-dancing mobile OS, ICS brings myriad improvements, including superior multi-tasking, better data management and the ability to unlock your phone using your face. Custom ROMs, on the other hand, are unique versions of the operating system created by the many passionate and talented coders working within the Android community to bring benefits beyond the official OS.
It might sound scary, but it's no different from when a handset manufacturer or network operator creates their own Android skin. They take the core Android OS and tinker with the look, feel and functionality, thus creating an original experience. In fact, one of the big benefits is that these ROMs strip out all of the extraneous rubbish -- unnecessary apps and 'bloatware' -- that is often bundled with branded versions of Android. This can result in much faster performance.
I've picked out a couple of the very best custom ROMs doing the rounds. To install these, you'll need to have rooted your phone first. Thankfully, we've got a guide for that too. We also have a guide for how to install ROMs on your phone, so be sure to familiarise yourself with it before going any further.
It's also worth checking out the excellent ClockworkMod ROM Manager app, which is available for free at Google Play. This makes the process of installing custom ROMs much easier. It allows you to back-up your existing ROM should you wish to revert back. If you upgrade to the premium version of the app, it will even let you perform over-the-air updates for supported ROMs, just like officially sanctioned software.
It goes without saying that this level of tinkering is only for those of you who are 100 per cent confident of your hacking abilities. Messing with your phone's firmware instantly invalidates your warranty, so make sure you're wearing your special 'brave' trousers before installing any of the ROMs listed below.
Also be aware that unlike Google and Samsung, the developers behind these custom systems don't have millions of quid and a workforce of thousands. There will be quirks with the software and you'll need to be patient in waiting for them to be rectified.
Easily one of the most popular custom Android ROMs and one of the few to receive positive recognition from handset manufacturers and network providers alike, CyanogenMod has been around since 2009 and currently supports around 60 devices.
The team behind the ROM is committed to producing the most stable and reliable firmware for your Android device. A whole host of cool tweaks and enhancements are packed in -- the vast majority of which have been influenced by feedback from the 1.7 million users who have downloaded and installed this custom ROM. The music player is a particular highlight -- so much so that it's been released as a standalone download for rooted phones that aren't running CyanogenMod.
Security is another thing the guys behind CyanogenMod take very seriously, and that's why the ROM includes the ability to revoke individual permissions for applications. You can also filter outbound calls and SMS messages using 'Phone Goggles', or 'drunk mode', as many people have called it. This feature could prove indispensable to those of you who regularly make prank calls or send provocative texts while under the influence of alcohol...
Created by Chinese firm Xiaomi Tech, MIUI is arguably one of the best-looking custom Android ROMs available. It's also one of the most radically different. MIUI drastically alters the way your phone's user interface looks and many people have compared it to Apple's iOS.
The most significant difference is the complete removal of the Android applications drawer, which makes the whole user experience feel much more iOS-like. Another bonus is the inclusion of support for themes, of which there are well over 100 community-created variants now available (although with the recently ported MIUI 4, themes aren't currently supported on the Galaxy S2, so you may wish to try an earlier version).
Like CyanogenMod 7, MIUI is based on Android 2.3 Gingerbread, although experimental versions of the OS have been released that are built on the Android 4.0 framework. These are still very much in the testing phase, so don't expect them to perform 100 per cent smoothly.
Resurrection Remix Pro
While mods such as CyanogenMod and MIUI have taken their time getting up to speed with the Android 4.0 source code, some of the smaller modding teams have stolen the march, producing new custom ROMs that offer subtle visual changes over stock Android, but considerable performance improvements underneath.
Resurrection Remix Pro looks very much like the bog-standard stock Ice Cream Sandwich interface, but additional options include toggle settings in your drop-down menu bar (like HTC Sense prior to version 4). It also strips away all the unnecessary rubbish that manufacturers and networks insist on installing on your handset, and this increases speed and overall performance.
If you're happy with Ice Cream Sandwich but are looking to gain a little additional power, this is a good bet.
This is another ROM from a small development team. One man, in fact. Even though it has been coded in someone's bedroom, SensatioN ROM looks absolutely stunning, boasting subtle yet classy enhancements over the existing Galaxy S2 user interface.
Based on ICS 4.0.3 -- which is just one version behind the latest 4.0.4 -- SensatioN ROM is undergoing constant design changes that should result in a package that's even more visually appealing than the current edition. Although it's not quite as well known as CyanogenMod and MIUI, this is worth keeping an eye on.
Foxhound Otacon Edition
Another Ice Cream Sandwich ROM that looks mighty similar to the stock experience, Foxhound offers some hidden benefits. The most obvious is overclocking, which allows you to boost the performance of your phone by dialling up the speed of the processor. This is fun for experimentation, but it also results in reduced battery life and random crashes, so you're unlikely to rely on it too much.
More appealing is the fact that Foxhound is quite a stable ROM and offers speed improvements that put the Galaxy Nexus to shame. Firing up the camera feels much quicker and the phone seems to respond really well to general commands. If you don't resort to overclocking, you'll also notice that battery stamina is improved over the official Galaxy S2 OS.
Another bonus is that you get a cool boot sequence inspired by Konami's Metal Gear Solid series of videogames -- from which this ROM also takes its name.