Keep in mind I have spent tens of hours trying to correct these issues via various ROM's, Modems and Kernels, including KH3 which was the best.
My issues were as follows:
-Wifi can't connect at any McDonalds wifi. Works at starbucks, sometimes.
-4g/3g uploads always dip in the speedtest chart for 2 seconds then bumps right up
-Wifi sometimes says connected but doesn't actually work. Didn't happen too often.
-banding on the screen, blobs on screen in dark room/black image on screen.
-phone was warped, determined I just had a bad one as all the other ones at the store were perfectly flat.
-call volume extremely low even when using the secret code to bump it to 100%. my loaner phone a motorola droid is twice as loud as the s2. I can actually hear my girlfriend talk to me now and not have to say what? pardon? every 2 sentences.
-people can't hear me in calls if i'm talking in a low voice, like anyone would at the end of a long stressful work day. even with noise reduction off.
-stock rom has under 6 hours battery life under medium use, easily fixed with custom rom, but still it shouldn't be a necessity to void your warranty untill official firmware is released for your provider, just so you can use your phone for more than 6 hours.
-phone gets hot, can be solved by undervolting cpu/gpu.
Please confirm if you are also having these issues, to help me make a decision regarding what I should do when the phone comes back.