I don't remember having a high registration time for my .is domain, although its possible I just forgot.
The only gotcha I would mention if you go through isnic is that you need to have your own DNS servers, and they have to be registered with ISNIC with a NIC handle (and some other things?). I just use Linode's DNS servers (where I host it), and haven't had any issues.
Have you used their vps service? If you have please comment on its reliability, seems very competitively priced. According to wikipedia 100% of Iceland electricity is produced from renewable sources. I am tempted to move most of my servers to Iceland.
The only gotcha I would mention if you go through isnic is that you need to have your own DNS servers, and they have to be registered with ISNIC with a NIC handle (and some other things?). I just use Linode's DNS servers (where I host it), and haven't had any issues.