As I said in the other thread, I'm kind of in your boat. I played a TON of 2e and 3e, both as player and GM, and a tiny amount of 1e (I got into it at about the 1e->2e transition, but I did have the 1e books). The 4e ruleset seemed to me to be a lot of changes to rules that more-or-less worked, for no real justifiable reason.
The new rules look okay, the character creation rules leaves clear room to grow (in 3e, the improvement curve seemed much flatter: you started out superhuman and just got a little better over time). But the change to the core mechanic success rolls just seem weird. I liked the rule of 6 and having crazy-high target numbers just for weirdnesses.
There was a rumor going round the 'net that 4e was going to be a d20 port, back when it was being worked on. Frankly, I'd be happier with SR using d20 rules instead of what we have now.