I've been playing on ICS for a few weeks now and what I learned was that you have to be willing to branch out from the base ROM and try some modems and kernals. I was amazed at the difference from one modem to the next, not only in signal strength, but the battery life can vary by a factor of 3 or 4 between modems. I have to agree that the Slim based ICS Roms have been the best for me. I recently tried "Nostogia" which is built on top of ICS. I flashed it but the modeme was no good in my area. A simple flash of the UGKC1 modem gives me 1-2 days battery life and GPS that actually works well enough that I trust it! I have never trusted the GPS before but finally I have this phone working so well I think I'll keep it till it dies! BTW, if you like the colorful look and feel of the Gingerbread ROMS, then Nostogia is what you want. Slim is pretty plain to look at but when you use the Nastogia Slim ROM, it really makes the transition nice.
ROM: AoCP 5.6 (Since 4.16.2013) Get it here
Kernel: Stock AoCP
Modem: radio-cm7-ics-captivate-ugkg3-signed Get it here.
Launcher: Apex Launcher
(from the play store)
Current Issues: None with my phone, plenty otherwise!