I just flashed teamhacksung's CM9 ALPHA for Captivate (BUILD 16) today and am very happy with the performance:
[ROM][ICS][IML74K] teamhacksung's CM9 ALPHA for Captivate (BUILD 16) - xda-developers
Previously I was running the latest nightly build of CM7.1, ie, cm_captivatemtd_full-181.zip. Last week I tried flashing Team ICSSGS [Android 4.0.3] RC4 twice, and had to go back to CM7.1 due to slow performance in general and browser slowness in particular. Then today I found the teamhacksung's CM9, and tried it, and is impressed by its performance on my more than 1 year old captivate.
The installation is very easy for me upgrading from CM7.1. The only thing to keep in mind is, after flashing the zip file from the download link on the xda page:
ROM Manager was unable to download Google Apps, so before flashing the zip file, download Google Apps from Rom Manager. Once these two zip files are on internal sdcard, follow the original instructions on the xda page to flash the update file, then repeat the step for Google Apps except skipping WIPE (wipe data/factory reset + wipe cache partition).
Before I started upgrading, I backed up my apps and data using MyBackup. Afterwards, all the apps and data can be restored. The only thing not restore is Adndroid Home, and maybe System Settings as well. Other than that, things are very smooth. One added benefit for me is my phone is now able to connect to computers with the USB cable, a problem I had for a few months without knowing why. I had just copied a folder over 4GB from my phone to a PC. Previously just copying a small file would disconnect the USB.