I bought it Friday but waited to do the install till today just in case there were major problems reported. I have a relatively new MacBook, a 13" I bought back in January, which is now considered a MacBook Pro. The install says it can take as quick as 45 minutes, but when it started estimated it at about an hour. Finished in just over 51 minutes. VERY quick install. I got back about 17 GB hard drive space after the install. But remember some of this space is because Snow Leopard measures capacity different than it used to. For instance, before I started my HD capacity reported 206.88 GB, now it's 222.13 GB.
I'm liking the new Expose feature, too. It's supposed to speed about boot and shut down times, too.
Love the new look to Quicktime and the new clean playback window.
UPDATE: Wow, Safari with the new 64-bit architecture is noticeably faster! That improvement is almost worth the $30 upgrade cost itself!