For my money, no, but it's really only something you can decide. Still, I would say that just by asking this question you've already answered it for yourself. You've likely been to a store or two and compared 60 and 120Hz systems side by side and been unable to discern any real difference. So I would say that odds are, you're not going to really see any significant change in gaming.
I would say 60Hz is perfectly adequate for all types of gaming. However, 120Hz would probably make for a slightly better overall experience if you're into games that are "busy" and have lots of things blowing up or flying around. Whether or not it's worth the difference in price on the two sets you have to answer for yourself. And again I'd suspect not so much, because if you had any real doubt, you'd just get the 120Hz system, but you should decide for yourself regardless.
I'm trying to pick between a 60 and 120hz hdtv. Does it really make that big of difference?