This is a REAL problem with this phone... Don't let anyone tell you any differently! I noticed it the day I took it out of the box and turned it on. Since then... almost 2 months later... after extensive side-by-side testing with WiFi Analyzer and other Android phones (Droid X2 & HTC EVO 4G), as well as also using a co-worker's GS2 (to ensure it wasn't only MY GS2), I can 100% confirm that the WiFi reception in GS2 is most definitely compromised!
I don't mind not seeing "full bars" if/when I do a Speed Test and still obtain expected speeds, which is generally the case when I'm seeing 2 or 3 WiFi bars. However, the real problem (also described above) kicks in when I'm in my home and/or office and only have that 1 "dot" of WiFi signal... enough signal to be connected, but not enough signal to WORK! --- The really sad thing is that this "Single Dot" issue occurs in parts of my home and office where I was getting full strength WiFi signals on my 2+ year-old Palm Pre "Minus"!
I surely hope Samsung/Sprint are "listening" and that there is some possibility of a "fix" for this. I have finally left my WebOS obsession in the past, and am beginning to embrace Android and the GS2. However, this WiFi issue is almost a "Deal-Breaker" for me!