I am very happy with my iPad one but if I were to buy an iPad today it would at least be a iPad 2 because of the operating system upgrading I have a feeling that the first generation iPad will not get ios 6 and even if it could I am not sure I would update. The iPad barely made it through the 5.0 upgrade. For browsing and email the iPad one is fine. It depends on the games you want to play. If they are memory intense games I would get a higher iPad.
I see what you are saying with being upgraded but for what I would use it for, web browsing, email, some light games, and watching videos, would whether or not it got upgraded really make a difference?
I still have my original iPad and don't have any issues out of it. Sure, browsing can be a little slow at times, but it's not worth spending another $500 to load a few websites faster. I'll stick with my iPad 1 till the 4 comes out next year. I do; however, always upgrade my phone to the latest available model. Keeping my phone fast, since it's my main device, is more important than my tablet.