I didn't have any problems. I put on about 15 machines in my network plus my two DC's. The only issues I know of is if you are running some older 3rd party program. It may not work afterwards. Make sure you select ARCHIVE FILES so you can rollback.
Don't know of any offhand, but search the forums here and there just in case. And as always, you can choose the option "archive files" so you can uninstall it. I'm running it right now and it's pretty smooth, no hiccups here.
Yeah, that would be due to the new Blaster worm pounding it. Keep your eye on the news for when this all blows over. Or go to Win2k's service pack page and download either the express install or the network install. The latter may be a better choice, but you'll want to let it download overnight.
The only problem I'm aware of is if you're running Miva Merchant on a Win2K system. If you've got a 3.x+ version of Miva, you need to make sure you're running the latest version of Empressa or you're have random crashes.....trust me.
I read some bad things about it when used with Citrix Metaframe, so that's why we don't put it on our servers at work, but we're installing it on new users's workstations little by little.