1. The most common problem in Xperia devices: music playing sudenly stops while browsing with chrome or other browser. Pressing "pause/play" button does not help, have to restart the player. Happens in all players, including Walkman. Most common solution is to do a clean firmware reinstall.
Steps:
1) backup everything (i use Titanium Backup pro, root required)
2) download Sony Update Services tool: http://www.sonymobile.com/gb/tools/update-service/
3) run it, follow the steps on screen
4) wait for applications to auto-reinstall, restore your backup users data, enjoy.
UPDATE: it helped only for a while. after i some useage, especially, the software reinstall, the problems repeat. V6 SUPERCHARGE script did not help either. Only option is to use OperaMini.
2. Second most annoying problem, is not sufficient music volume in headphones. Most people say, that is done by manufacturer on purpose due to some law and sanitary restrictions to prevent ear damage. Well, if you are no afraid of ear damage, you may try apps like Volume+ (Sound Boost) in Play Market. (needs root) -- results vary. Personally I used this: http://forum.xda-developers.com/showthread.php?t=2370047&highlight=volume+boost . But the next thing works also good.
3. Music sound enhancer: I recomend Viper4Android (root required, /system remount fix also needed): http://vipersaudio.com/blog/, far better than anything built in. Install the driver in normal mode, use "force" install, plug in the headphones, go into Settings -> Sound -> Sound Effect and choose Viper4Android. Afterwards it works in every player app you have. If the phone spontanously reboots, see the /system fix below.
4. Folder play: Walkman is neat, but it cannot play music by folders. Use "Rocket Player" (more feature rich) or "FolderPlayer" (simplier, faster) instead. MX video player is beast for video.
Otherwise, its a great device! The first time i do not want to experiment with firmwares. Besides, Android 4.3 and Android 4.4 official updates are promised! Tested its LTE with Russian BeeLine provider -- great speed!
Prerequisites for the above:
- root: http://forum.xda-developers.com/showthread.php?t=2405933
- /system rw remont fix: http://forum.xda-developers.com/showthread.php?t=2317432 -- that is the most frequent reason for sudden device reboots for most Xperia devices. Fixes the Viper4Android issues as well
- FlashTool: http://www.flashtool.net/download.php - required for above.
- xda: http://forum.xda-developers.com/xperia-sp
- xperia blog: http://www.xperiablog.net
UPDATE 20.03.2014: I hoped that update to v12.1.A.0.266 with Android version 4.3 would've solved first to problems, but it didnt
