Well...some extra stuff. Boot time scanning is only for NT based machines. Not sure about NT4. I haven't tested that. But with XP and 2k, there it is. 9x, there is no boot time.
Also, dial-up users seem to have problems sending out large emails. So, I recommend, disabling smtp scanning if you are dial-up.
I recommend the following with the scanner. A boot time scan, a safe scan scan. After that you should be fine.
Oh, and I have see some machines do a boot time scan. "Kill" some virii, then boot normal, and find more viruses.
Personally, I like Avast!. I'm using pro right now.
The company that has avast has a few other programs they are using too. One is a recovery software that sux comapred to winternals ERC commander. Another is a network based virus scanner.