We have been with PatriotNet (www.patriot.net) for a number of years. Overall, we are very happy with them. They aren't "unlimited," but you can do "whatever you want" with 300 hours a month of PPP access. Telnetting into your shell account *is* unlimited. PatriotNet is based in Fairfax, VA, near GMU (George Mason University). Support is pretty quick, helpful, and intelligent.
History of MNS problems: We shopped around for a long time to find a flat-rate, unlimited-use provider. We finally decided, back in December 1995 or so, on MNS. They assured us that we could stay logged in for as long as we needed, as long as it wasn't all month or something.
MNS says they are unlimited-use, but they're not--if you stay logged in for more than 24 hours straight, they try to close your account or make you pay for a dedicated PPP line... They don't say anything to you before closing the account. They close it and wait for you to call them to see why you can't log in all of a sudden. Then, after talking to several different people (all of whom say they don't know what the problem is), it'll be reopened. Then you'll get e-mail from them saying the account has been closed.
They send no e-mail *before* they close it, saying that you're doing something that they'd like you to stop. No phone call or snail mail *when* they close it. And to top it off, they close it a few days *after* whatever it was you were doing.
What were we doing? Well, the first time, I was using sendmail at the command line. They said I was hacking. This happened once that they cared about. The second time, my husband was downloading some X11 files and we left the connection up the whole time (about 72 hours). This happened once. Three days after we had closed that connection, I couldn't get into the account...
I am no longer arielle@mnsinc.com because of their shoddy support and service. I advise everyone to stay as far away from MNS (Monumental Network Systems) as possible.
Feel free to e-mail me for more details...