Having owned a galaxy tab 7.7 for a few weeks now (ordered from Hong Kong), perhaps I can chime in. Galaxy tab 7.7 vs ipad 2/3 all depends on what you value and consider important. There is no perfect tablet, so no matter what you choose you'll be gaining something and losing something else.
The 7.7 is smaller, lighter, and thinner than any other high end tablet out there. It also has a better screen than anything else out there. IMO even the iPad 3's screen will be inferior. I don't care what the resolution of the 3 is going to be, the contrast, color, size and power consumption of OLED displays are superior than any other technology currently in production. When OLED tv's come out in 2012, you'll be blown away. I am a home theater geek and have always been searching for a display with a 'perfect' image, and let me tell you OLED is amazing. To me everything else looks like crap compared to my 7.7. 12+ hour battery life (of continuous use) and an incredible picture is something you just have to experience for yourself. Not to mention it's light enough to read with 1 hand, similar to a Kindle. I read on this thing for extended periods of time so I appreciate the size of the 7.7.
Having said that, the performance of the software is crap. Not unusable, just annoying. The lag is there, something my Epic 4g Touch (I hate these long names) doesn't even experience. I am hoping the ICS upgrade in the next few/several months fixes this. iOS is way more polished on the iPad 2 compared to Honeycomb+Touchwhiz on the 7.7. The apps don't compare either, way better on iOS. I would expect that to change in the future with more and more Android tablets on the market, but I hate predictions, especially about the future.
All that to say, when the iPad 3 comes out I'll play with it and see which one I keep for good. Do I want amazing hardware, or amazing software? If the iPad 3 had an OLED display, I'd get it in a heartbeat. However I don't think there's any way they could acquire that many panels in a short period of time before launch. It's just too new for iPad-scale production.