Personally, I disagree with anyone who says that Lucas has made any truly significant changes to any of the OT. Just minor stuff that only the geekiest of the geeks will complain about.
Precisely. I've never had a strong preference one way or the other regarding the various editions of the original trilogy. I can probably pick individual moments that work better in one edition or the other if I think about it (by default, CGI Jabba in
A New Hope works better on the 2004 DVDs than the 1997 Special Edition, for example), but mostly it's not a big deal.
As far as the notorious Han-shooting-Greedo business goes, Lucas' excuse that they didn't have the time or money to insert the last blast showing Greedo firing is at least plausible - watching the original blast, one doesn't actually see Han's muzzle flare either. But it was added a trifle awkwardly in the special edition, was improved in the 2004 DVDs, and is not profoundly upsetting to me either way it's done.
Oh, and replacing the
Phantom Menace Yoda with a CGI equivalent is long overdue, if anything. That puppet was distinctly inferior to both the puppetry of the original trilogy and the CGI model of the subsequent films, and the clip I've seen of the re-CGIed Yoda... just reacts bloody better than the puppet did.