My computer always boots a little slower right after a required restart after installation -- it's probably because I've got the ojurnaling option turned on for my drive, and the journal is being updated to reflect the recent changes to the files on the hard drive (which could number in the thousands for an update like this). Subsequent restarts are much faster.
No problems here at all, though I might mention I downloaded the combo updater and ran that as opposed to getting it through Software Update. No problems downloading... greater than 300kbps/sec here in Texas on a 3.0Mbit down/384k up DSL connection.
No noticeable changes, although I read through the updated items list and almost none of them apply to me. No iPod for USB2, all my peripherals have always worked just fine since 10.0, and I've never had a problem with a hacker or some malicious exploit (and if I did, a clean reinstall would fix me in under 1 hour -- no critical data is stored on my boot drive).