Looks like the just-released Samsung Epic 4G Touch is dealing with a few new-device hiccups. Both issues are relatively minor, but are noticeable (and annoying) nonetheless.
For starters, the calendar app may (or may not) force close when multiple events are dismissed at the same time. Secondly, if you're using 4G hotspot and take a phone call, it will kill the 4G connection. Of course, you can easily just re-enable the service at the end of the phone conversation, so it's only a minor inconvenience.