Hi, I just recently converted and I am loving it all the way. Go with Helmi's AKU3.2 ROM as it has given me very little problems, other that the need to just make sure that I read and understand the guide first.
I did find the phones operating speed somewhat slow, but then that is to be expected from a installation that was not meant for the phone. Same thing happens when you upgrade a PC witha new OS and it goes a bit slower. But what you can do is to help it a bit and what I did was to spend around £14 on XCPUScalar and overclocked the internal chip from the standard 400mhz to 530mhz. It is so easy to do, all you do is to install the application and then slide the slider to the required speed. It does mean that my phone battery does go quicker, and I have been trying out different scenarios and whereas during normal use, ie 45 minutes of mp3 listening in the morning and then again in ther evening while on journey to work, and around 10-20 calls a day, the battery used was around 75-85, now it completely drains my battery unless I use my spare.
The best thing to do is to invest in a USB data cable which charges the phone at the same time and even if you have a laptop, you can still charge the phone during the time that it is in the cradle.
The XCPUScalar does have a dynamic speed changing capapbility which basicaly changes the speed depending on CPU percentage used, but I found it slightly sluggish to kick in and just so much easier to stick it onto the 530mhz and just take my spare battery with me.
Now that I have it at 530mhz it works even better that I had hoped, all the functions and compatibility and even works faster that my previous 2003se.
Be careful thought that the process of upgrade may take a few times to get right, so make sure that you have either the whole day to spend on the upgrade or you have a spare phone to hand.
Extra tip, and very important, dont use a external USB hub to plug your phone as when you come to upgrade it gets stuck on the OS Upgrade screen and like me you will have a heart-attack until you figure out what the problem is...
Hope that helps.