And I won't even go into the recumbent's tendency to wobble on the road (at least, the model Phil rides). Or its extremely low profile, making it vulnerable to traffic.
Anyway, I know there are plenty of hard-core recumbent fans out there, but I'm not one of them. I don't think they're nearly as fast as advertised, even on level pavement. They're heavy, and typically expensive due to the near-custom nature of their construction. I think many recumbent riders secretly hate their bikes, and put up with them only because they've sunk $3,000 or $4,000 into them and can't bear to admit they're wrong. That, or they just want to be different.
Of course, there ARE good reasons to ride a recumbent. I don't dispute for a minute that traditional bikes come with serious ergonomic problems, although the sore butt and shoulders you mention typically dissipate with riding time. Recumbents are recommended for those people whose back or prostate problems make a traditional bike extremely uncomfortable. Keep in mind, though, that recumbents also tax the body in certain ways, and some recumbent riders have said it has taken a year or more to really get accustomed to the bike.
As for which bike, my only advice is to try a few and see which one is most comfortable. Longer wheelbase would be more stable and track better, of course, but a short one would be more maneuverable, which I think is an issue. The big difference in design seems to be how you steer the bikewhether with handlebars that are chest-high, or with steering bars that are placed low. The Longbikes Eliminator ($2,600; www.tandembike.com) is an example of a short-wheel, low-steering bike; the Rans Stratus ($1,600; www.ransbikes.com) a long-wheelbase, upright-steering model.
And all you recumbent riders out there, save your breath and your hate mail