[XPERIA X10 Q&A, Help & Troubleshooting] Dr Goodvibes:
Yerp, Install stock Sony Ericsson GB 2.3.3 and then use the latest version of flashtool 9.10.1 and just root the phone using zergrush exploit.

Remember to enable USB Debugging and known sources first.

You can then install CWM or xRecovery via flashtool once rooted to get yourself started.

ROMs and Kernels can then be installed as instructed.

Oh, and you can use the S1 Tool to check your bootloader is unlocked.

Tutorial: Rooting, Bootloader Unlocking and Updating

I wouldn't install anything beyond a GB ROM as you'll lose HW Acceleration on your GPU.

If you don't plan to watch any 720p videos and won't rely on your GPU for any off-loaded work then an ICS or JB ROM on an XPERIA X10i may work for you.

If you read alot of the comments on ICS and JB ROM for the XPERIA X10i those that say it's brilliant or say thank you, never say why it's brilliant. What have they really gained, maybe some eye candy and do they really know what they've lost. :)

[note] - XPERIA X10i CM10 you do get WiFi channel 13 and screen Snapshot to mention a few things

Benchmarks show vast improvements in OpenGL 2.0 performance on XPERIA X10i CM10 ROM, but when you look at GPU FPS it's lower than stock GB 2.3.3

3DMark benchmark may provide some interesting results when it arrives.

I've used the Epic Citadel game demo benchmark and get 11.2FPS using GB 2.3.3 and with XPERIA X10i CM10 (Android 4.1.2) ROM I get 11FPS so there's no real gain.

GPU FPS on GB is around 54FPS, but with XPERIA X10i CM10 ROM that drops back to 43FPS.

If your XPERIA X10i 'media' player is just going to play mp3s you don't have to worry about GPU HW acceleration and your can ignore my little GPU rants :o

I have DoomKernel v6 on a stock GB 2.3.3 ROM(all /system/app bloatware removed) with XPERIA S apps on stock V2 and BEATS

This is not strictly a 'media' ROM however it's got the latest XPERIA S GB Apps which include a stock music player with equalizer which sounds pretty good for stock and does play wma,mp3,ogg but not flac. You also get a later version of the Sony home launcher which also includes the ability to rotate the home screen.

Another supported option is DonutHD ROM

I installed Neutron Music Player(Play store) which plays wma,mp3,ogg and flac ALSO if you have CIFSManager(Play store with cifs.ko supported by DoomKernel) installed it'll allow you to include a NAS(Network Attached Storage) or external storage as if it was local storage and thus allow humungous Music libraries.

OpenVPN(tun.ko supported by DoomKernel)/PPTP, WiFi Hotspot and Samba FileSharing( can be seen by almost any device) round out a raft of connectivity that allows the XPERIA X10i to be both a media client and a media server.

If your media includes 720p videos, I'd stick with GB based ROM as my experience is that nothing beyond GB supports GPU HW acceleration and that 720p videos will be unplayable.

However, that said, if they ever get GPU HW acceleration working in say XPERIA X10i CM10.1(Android 4.2.1) I'll be among the first to upgrade. How insane would that be. :D

BSPlayer(Play Store) is the best video player for the XPERIA X10i for viewing the likes of .mkv(H264,AC3) 720p videos which will use HW acceleration both on local videos and those streamed across your LAN.

If you look for TVHGuide.apk and have a network attached digital TV(somewhere on your WiFi network) the XPERIA X10i will quite happily play 720p and SD TV, but NOT 1080p :(

I have a 32GB SanDisk MicroSD in my XPERIA X10i which is very stable, but I'm considering trying my luck on a 64GB SanDisk (Results could/can be unpredictable)

Mugen Power do a good line of extend life batteries. I have a Mugen Power 1800mAh battery in mine, but if you're looking at a home 'mobile' media player, then there is the 3600mAh battery with enlarged back cover.

On the SIM side AND if you're brave you could tear down the XPERIA X10i and check the contact pins in the SIM slot all make contact with the SIM card.

I had a MicroSIM in the SIM slot at one time and when pulling it out it jag'd one of the pins and thus it didn't make contact anymore,

By gently 'lifting' that pin I was able to get my SIM card(s) working again.

I tend to like my XPERIA X10i over my XPERIA LT26i... how weird is that. :D