Slow and steady definitely sounds about right for me. Can't keep a paceline for anything but maintaining an average 15-18 MPH for the 25-30 mile rides I'm regularly doing now isn't too hard - and is a heck of a lot of fun (especially finding parts of Cleveland that aren't ugly). Need to get it up to about 20 MPH average though before I'll be happy with my performance.
Then I have to find a way to make cars stop doing stupid things and convince Ohio-DOT that the edge of a road should really be better maintained.