Well, I think the answer to your questions is this:
Don't worry. The upgrade seems to be going well for most folks. If you are particularly sensitive to any bugs, waiting for 10.7.1 would be safer. But, my experience has been that 10.7.0 is fine. I'd say this is a judgement call, based mainly on how low your tolerance for issues is.
Regarding the 2g ram question, if you have an easy path to upgrade your existing system to more ram, do it. Boosting to 4g is enough for most casual users while pro users tend to need 8g. On a modern system, moving to 8g is inexpensive so I'd recommend that unless you have a system that can't handle it. In which case, grab the 4g upgrade and enjoy that.
If you would like more specific answers, posting more details about how you use your system, what model you have and what you plan for it will help.
