Got XSP with 4.3, .201 preinstalled. Crap experience as stutters and microfreezes were very common. Coming from LG Optimus 4X, I still feel a downgrade in term of UI. LG UI is miles ahead when it comes to customization and usability, Sony's too rigid, overly complicated and lacks certain useful options. Battery life - much better. Camera is comparable to LG. Hardware more capable (great Antutu score and Epic Citadel benchmarks), gets noticeably less hot.
Downgraded to rooted 4.1 generic UK with .254 kernel because of trashy performance of 4.3. UI is about the same, but runs smoothly and is responsive. Now, the battery life became really bad. I could put the phone in pure standby mode fully charged and it would lose 1-2% in 10 minutes doing nothing. Total of 10% lost during an hour of laying on a table in standby, screen off, no mobile data, wifi, bt, background services or programs at all. Even notorious-for-bad-batt-life Optimus 4X didn't have that much a drop under same conditions. No drops in GSM signal. When I check with BetterBatteryStats, I see a few wakelocks I never saw on O4X. Froze a bunch of apps and tweaked the system a bit, but that didn't help. I can get a day off the cable with modest usage, maybe.
Downsides of v4.1 compared to O4X on 4.1, besides already stated or widely known:
- No SIM contacts usage other than Import from SIM option, always and exclusively phone's internal phonebook active
- Less user-available RAM (766MB on 4.1, little under 900MB on 4.3)
- Bugfix updates that don't fix obvious problems
- Bunch of mostly useless bloatware
- A PC software like LG On-Screen Phone doesn't exist
- Overall configurability and customisability of the device are lower
- Charging takes forever. Even on USB port connection, O4X charged quite fast, and faster on supplied wall charger.
- More gestures/steps needed to perform certain operations in UI
- Liked the power toogles better on LG
- Lockscreen rigid on 4.1, can't put custom shortcuts on it.
- Sony trades you the bootloader unlock code for your phone's IMEI and they make you acknowledge your warranty "may be" void. There are methods to relock it, but I'm sure they keep the IMEI somewhere in a singular database accessible by repair shops, so my guess is that you can kiss your warranty good-bye.
- More complex root procedure, and tiresome if you want 4.3 and unlocked bootloader afterwards
- I don't use OTG or MHL and there's no LTE where I live, so, at the moment, that does nothing for me.
I could go into even greater details, but that would require much time and space, and this is not the place for it. Haven't yet came around to install a custom non-stock based ROM, but I strongly feel I should.
To summarize, I thought the phone would be a step up to my previous one, but in reality I traded one set of problems for another. Gotta say I was happier with LG.