We tried SP1 from Windows Update on 4 machines (2 x86, 2 x64). One of each went fine, the x86 machines crapped out part way through the install and would not continue. Using the downloaded ISO, we ran the x86 standalone updater and finished without further issues. The x64 machine crapped out with what looked like a restart partway through the update. Try the standalone updater gave an error about an install already being in progress. Tried a couple of restarts and still no joy so re-imaged the machine. SP1 from Windows Update worked without issue then.

Testing on the same machines with the downloaded installer had no issues so at this time, we're blocking the update at local WSUS server. If anyone really needs SP1 or screams loudly enough, we'll do the manual update. Mass updating is going to wait till the next re-image cycle in about 4 months.

Testing on the updated machines did not come up with any problems with the corporate software load though some oddities such as NetScan showing unused IP addresses as responding.