[Sony Xperia P, U, Sola, Go] taboo5200:
If you're checking for updates with the phone's own Update center, then it will probably perpetually report that it's up to date - afaik it doesn't check for updates across Android versions (e.g. 2.3.7 -> 4.1.2), only those in the same version (in GB's case, the latest firmware is 6.0.B.3.184). You'll need to use either PC Companion or Sony Update Service to check for and apply updates.

As for whether you should make the jump, that's hard to say. I guess I could put it this way:

GB - Fastest version of Android ever on the phone, hands down. Extremely snappy response in all aspects, at the cost of the more advanced features that are only available in ICS and JB.

JB - Second in place to GB in response speeds (from my own experience), response in scrolling and panning, as well as the camera are negatively impacted. The stock bloatware is also more resource hungry and insist on running, needlessly consuming precious RAM. The upside is that you get the newest features, and - supposedly - better security. You also get a little more eye-candy with transition effects and stuff, but you'll have to give some things up too, such as the 3D camera.

You should also factor in the increased RAM consumption of hardware-accelerated apps (an extra ~8 MB

each

). It's not as much of an issue in GB as it is in JB since GB has lower overhead memory costs.

Also, keep in mind that updating is pretty much a one-way route - Sony provides no official means to return to your older firmware after updating, and you cannot backup the exact firmware you have in your phone right now. Fun, eh? You can, however, return to GB post update by downloading one of the older firmware FTFs floating around the web and using Flashtool to flash it into your phone (though there's always a risk that the image you're flashing might have already been maliciously tampered with, so it's really up to how much you trust it).

With regard to rooting, it's apparently impossible to one-click-root on both GB (yes, still!) and JB firmwares at this point in time, so you'll have to use an alternate method known by the name pre-rooting. While not exactly difficult, it is still a pretty tedious procedure involving flashes to ICS and stuff.

Please note that you do

not

have to unlock your bootloader to root the phone. I'm placing extra emphasis here because unlocking the bootloader makes an irreversible change to your phone - it eradicates the embedded DRM keys, and - in most cases - voids your warranty. PC Companion and Sony Update Service will also refuse to recognize your phone while the bootloader remains unlocked. You're probably wondering at this point, "So what in the world are those DRM keys anyway, and what's the big deal about them being wiped?". Well, for starters, some bundled software-based features exclusive to Xperia phones, such as Mobile BRAVIA Engine and TrackID (despite the latter being available on Google Play to any Android-powered phone - go figure :confused: ) will stop functioning as soon as the keys are wiped. To some, it's insignificant, but given the perfectionist I tend to be, I'm preserving them (then again, to each his own). The key (pun unintended) thing to note here is that

relocking the bootloader will not restore the DRM keys

- they're lost forever once wiped. Since the keys are only wiped upon unlocking the bootloader, it's entirely possible that Sony's tech support can detect that a phone's bootloader has been unlocked and relocked based on the presence - or lack thereof - of said keys (disclaimer: I'm not sure if they do actually check for the presence of the keys, so you might get lucky. YMMV) and reject warranty claims. Hopefully it never comes to that.