I was reading Sam Curran's blog and he was talking about intelligent server migration. This, of course, is interesting to me since I just got done doing the same thing. Sam had a more difficult situation in that he has users to make changes to the database. While that's true on a blog with comments, it wasn't a huge concern to me over a weekend.
Dealing with DNS really is the biggest problem. It took almost 48 hours for DNS changes to propagate to the point where the old server was done taking traffic. I think next time, if possible, I'll just switch the IP address on the server.
The biggest challenge I faced was moving to a 64-bit processor. I started out loading up Fedora Core 6 for 64-bit processors and trying to follow my instructions for setting up a Linux server. In particular, building the LAMP stack turned out to be a nightmare. Nothing impossible, but with the mental bandwidth I had to give it, I staled for 2 months.
Finally, I just loaded the 32-but version of the OS on the machine and everything fell into place. I was up and running in a few hours. I gave up some performance (how much?) for the fact of getting it done. The new server is performing well and has given a big performance boost to the compute intensive tasks like rebuilding pages and searching).