Man, opening the box to upgrade the RAM is a royal pain in the ass. I'm so glad that I'm maxed out now so I'll never have to do that again. I was positive I was going to break the thing the first time I tried to open it, and then I was positive I was going to break it when I was getting the case back together after I was done. Fortunately, it all appears to be in working order now, but I was a bit scared at the time.
Speed is pretty good, although not spectacular. More than adequate for what I want the machine to do though.
Tiger seems nice, although it's kind of lame that the machine actually came with 10.3 preloaded on it, so I had to do an upgrade myself.
The new Mail.app totally failed to handle my mail archives. The things sat there at 100% CPU usage for hours before I just gave up and went back to Thunderbird. Sorry guys, I wanted to give Mail.app a chance so that Spotlight would work with my mail, but rendering the entire machine unusable while the indexing process runs just doesn't cut it.
The RSS support in the new Safari is pretty cool. I'll have to build myself a cutting edge WebKit one of these days just for kicks. Haven't had time to try the new podcasting stuff in iTunes 4.9 yet.
All in all, I like the machine quite a bit. Highly recommended.