[Xperia Play Q&A, Help & Troubleshooting] illuminerdi:
I've used a LOT of the XP roms and first let me say this: there is no truly "best" rom, it all boils down largely to a matter of preference.

I'm currently running TrueAncestor 1.6 and I really like it, but I do miss certain things about ICS. The thing with ICS that's worth understanding is there is no truly stable or complete ICS rom for the Xperia Play. Every ICS rom has bugs or missing features. Some are worse than others. MANY ICS roms drop support for the touchpads in major games (EA Games, Gameloft Games, Rockstar Games) due to a colossal screwup on Sony's part. You can sort of regain the touchpad functionality using things like USB BT Joystick 6 or GameKeyboard, but those are hacks and they eat system resources.

Speaking of resources, ICS roms are also much more system intensive. Your phone will run slower, games will run less well, and your overall performance will be less snappy than GB roms. It's not *terrible* for sure, but Overclock is practically necessary for ICS roms to help make up for that performance loss. The XP's hardware is dated (it was dated when it launched, technically) and it's starting to show. The paltry amount of RAM and single core processor really hurt it's ability to run ICS and still kick ass at games.

Overall though, as far as ICS roms go I'd recommend AOKP, though the dev has gone dark and not updated it in a while. It was pretty good and had a lot of nice features. I hear CM9 is also nice, and it continues to get active support and development, and will eventually be superceded by CM10. Even then though, I still ran into moderate bugs on both of them - AOKP had a persistent problem where the WIFI would stop working due to a bug in the Settings dialog, so turning on/off your Wifi could cause it to stop working altogether, and the only fix was a reflash. It was a major pain in the ass. Other ICS roms will just randomly crash or reboot, or programs won't work or will crash that should otherwise work in ICS. Overall, be prepared for instability and don't expect 100% from your phone with virtually any ICS rom installed. Blame Sony for only releasing a beta of ICS and then dropping support.

There are other good ICS roms, such as ICS++, Ice Cream Sony, and KA, but some or all of those might have lost dev support (it's been a while since I checked) and none of them really did much in terms of feature changes/support, so they've stagnated compared to more active roms.

Honestly, I realize now that there wasn't a ton in ICS that I needed, and having switched back to GB last week I'm very happy I did - performance is better, battery life is tolerable (slightly worse than AOKP was), and games run great, plus I have full touchpad support again. It looked nice, but it didn't really add anything, and the bugs and missing features finally pushed me away from it after almost a year of running it (I've been running ICS since the first ICS ports hit the XP).

As for GB roms - TrueAncestor is good. I was running JokaWild for a bit, and it was ok, but it didn't blow me away, TA's theme is more preferrable to me. I'm running DoomKernel v14 which seems ok - it's also a bit dated though and Doom could probably do some updates to improve it a bit more if he had the time, but I'm sure he's quite busy.

I hope this helps - and good luck.

Also, if you aren't Fastboot enabled, get that done - it's worth the money and you'll need it in the hunt for the best rom, otherwise your selection will be very limited.