As far as your computer being newer, I have installed the "beta" that Microsoft officially released, well one of them (they are time coded to disable eventually, I think June of next year, I may be wrong on the date though) on a 1.2 gig computer I have here with 512 megs of RAM and it runs just as fast as XP does on that hardware. Haven't unleashed it on my newly bought (read, it was being thrown away) 2.8 gig P4 system but will eventually. I just don't know if there will be sufficient reason to upgrade really.
I am the type that upgraded from Windows 98 shortly before coming here 2 years ago. There was just not enough software that I couldn't use to require me to do the upgrade (Publisher 98 finally quit working so I bought, yes, paid for, a new copy of it) and I had to upgrade my Windows too so I just got an upgrade from a local vendor for $40 (legitimate, not a copy).
I have played with W7 and it looks nice and plays well but I just don't see upgrading right away. Good luck if you decide to. If done right, you may be able to pick up your new computer (if editing video in HD, I would go with an i7, costs more now but the amount of time you will save waiting for encoding will make up for that-remember, you can get more money, you can't get more time in life) and get W7 installed too.