I'd say if you can't get onto Napster at Uni, it's definitely been locked down port-wise - at the firewall. I am (partly) responsible for the firewall at the company I work for. If you want an idea, go get TPF (Tiny Personal Firewall). It's free for home use, and I consider it necessary - especially if you're on cable. For instance, I can let file sharing through, as long as it's connecting to Napster or Gnutella, and at the same time block people trying to ping my IP.
As for the OpenNap servers (and Gnutella as a whole), I believe the networks are protocol-based. In the case of Nap servers, the owners - private or commercial - can be targeted, which is what makes them vulnerable. Gnutella however, has a much more distributed architecture which you can think of this way: When you fire up a Gnutella client and are online, you are effectively equivalent to a Nap server. That's what makes Gnutella so powerful - imagine if all the Napster users went to Gnutella, there's no way anyone would be able to police 20 million "servers".
I'm currently evaluating BearShare 2.06 (or something) but I miss Napster's search power, especially with the ability to ignore words, and specifying bitrate minimums. I'll probably be a Napster user 'til the last stake is driven through the last Nap server's heart - unless some other software zooms up with superior features. Then I'll be the first rat to jump ship.