Several people have posted back saying they are having issues with alerts from store.exe after applying Exchange SP1. There's also problems with OWA now requiring a domain name when logging in (requiring DOMAIN\username where username was OK before).
To make a long story short, we screwed this up. We should have had these problems identified and a workaround/fix available at the time Exchange SP1 came out. I've gotten several rant e-mails from those of you whom I know personally, and you're all 100% right.
Right now, we're working to make sure there aren't any other issues with Exchange SP1. Right now we're working on getting everything wrapped up so you all can have something to fix all this. But here's what you can do right now:
1. For the OWA issue, work around it. Sorry. There's a partial workaround by placing the domain name in the default domain field in IIS, however the OWA cookie auth introduced in 2003 doesn't fully take advantage of this, so you'll still get some weird behavior occasionally. The best thing to do is use DOMAIN\username for the short term.
2. For the alert about store.exe consuming more memory, you can ignore this error. Store.exe is not really taking more memory - in SP1 Exchange changed the method in which certain memory bytes are registered (See my earlier post on this), which triggers this alert, but it's benign. What's probably even best is to just disable the alert altogether. We're actually going back to figure out why we put this alert in in the first place - we're going back to SBS 2000 and there may have been a valid reason back then, but now it just seems like an old alert that got grandfathered in.
You can install Exchange SP1 on SBS, and if you're comfortable with these issues, go right ahead. We're working to get these particular problems cleaned up ASAP, and I'll have more details on that as soon as I can.