Toni, I agree with the Sorrento crowd, more to see/do and very convenient to your other destinations. However, just to throw another choice into the mix, have you looked at Praiano? That's where we'll be staying the next time we go to the Amalfi Coast, not a typical tourist destination (which is why we want to stay there) but still very convenient to other towns. We actually were planning to go there this month but I was offered a free stay at the Four Seasons in Florence so we'll be heading north instead of south when we leave Rome next week. I'll be updating my website quite a bit after our return at the end of April, stay tuned.
Another beautiful, spectacularly romantic place to stay is Ravello. Very quiet, perfect for 3 days, just not as convenient to the other towns. We stayed at the Caruso but there are several less expensive (but still nice) choices there. If you choose Positano, take a look at the Palazzo Murat. I have been to il San Pietro and agree that it's beautiful, but really inconvenient for the way we vacation (ie, strolling around town, dining at different restaurants every night, etc.). For me the San Pietro is more a destination where you don't intend to leave, where you just want to plant yourself and relax vs. explore, and you really would want a car if you stay there. I'm with Libby, I am NOT a fan of driving on the Amalfi Coast road... I prefer taking ferries between ports or hiring a driver vs. renting a car. We've done it twice but aren't anxious to do it again... too stressful for a vacation experience IMHO.
So exciting! Now I wish we were going there on this trip!!! PM me if I can help out any more.