I've had an xperia ARC S for a while, which has been alright, but it's piddly 420MB (!) internal memory was a constant pain in the bum, because as soon as you put a couple of apps on it it's memory is full. So, over the weekend (after much deliberation because i'm rubbish at this kind of thing) I rooted it and installed 'Link2sd' and used 'Partition Wizard' to create a 4GB Pseudo-internal memory on the SD card, and now everything I download goes through LINK2SD, directly onto the SD card, the end result of which is never having to worry about internal memory capacity again.
Then I thought i'd go the whole hog and install a ROM (Xperia Ultimate HD V3.0.2, and Eagleboy Mod). I messed up the install the first time and 'Bricked' my phone (completely my fault; I thought I knew better than the instructions. Turns out I didnt). After a couple of frantic hours I managed to bring the phone back to life and start again, following the instructions this time and it was very straight foward.
It now feels like a completely new phone. The ROM has stripped the phone of all it's bloatware meaning it's faster than it was before and I now have Basically an Xperia Z, with its features, in an Arc S case! (apart from the Z's Processor, of course)
If anyone still has an ARC or ARC S, I'd recomend Rooting and Romming. If you do fancy giving it a go, i'd be happy to give you the links to the instructions that I used.