No not really. I'm having trouble understanding the off-line mode of explorer and off-line files behaviour myself. Sometimes when the DHCP renews ip-leases we have clients that go into offline mode even if they still have the same IP. You could try to see if interaction with explorer helps, or a short unplugging of the network cord helps.
We tested exchange internally about two-three years ago, and had rather large problems with the setups and limitations. Microsoft is good at making large software, but they have very little feel for the concept "good-enough". Many of my customers though have exchange installed through SBS, and the only real problems arise when a server crashes, or the hassle when someone leaves a company and he/she wants the exchange data to follow them out of the company.
Kind regards / Peter