I agree pretty much with S.Suikun. All the "improvements" feel more like new and flashy for the sake of new and flashy. They may be doing things in an improved and updated way, but whether it's better or not depends on who's watching.
The first thing I can think of that I like better now than in the beginning is the character design. As someone said, most of the older seasons' characters were extremely pointy, and their pupils were exaggeratedly eliptical.
For the most part, though, I prefer the older seasons' visuals to current ones. When everything is too bright and too vivid and too CGI-y, it becomes more a dull pain to watch than when it's all hand-done and artsy. To me, anyway.