The RCA's are very reliable, very easy to troubleshoot. Also they keep up constantly with improvements in the field (like newer DOCSIS standards).
Modems are provisioned on the network by MAC address and serial number...type on of those in wrong at tech support and you get a provisioning problem. Also sometimes for no known reasons the provisioning just goes bad and everything has to be wiped and started over.
Troubleshooting will be ugly, ugly, ugly...and unless you do it you'll never get anything changed from @Home. Yes tech support can be a bitch, but unfortunately they have rules they're stuck with before they can get you fixed (although I strongly recommend getting past tier 1 as early as possible and working with tier 2 (no offense tier 1, but tier 2 can do more).
Also (and I'm sorry, but this is an ABSOLUTE), there will be no troubleshooting until your setup is:
cable modem straight to one computer with no firewall or proxy software installed.
No gateway, no router, no switch, no zone alarm, no ics, no multiple nics, nothing. Troubleshooting is completely ineffective until you're in this configuration and tech support will not even talk to you until you are, seriusly they'll tell you to do it and call back.
They'll need to answer some basics - always been like this? what're the modem lights doing during an outage? any pattern to the outages? static or dynamic addressing? a bunch of other stuff. I could actually walk you through a lot of the troubleshooting, but I don't have access to @Home databases any more to check the provisioning, current IP, or repush accounts.