I'm trying to find a good saddle for my Cervelo S1. I've tried several, but I'm a bit confused. Are good road bike saddles necessarily hard? All the hard saddles I've ridden (none of them very far, though) have been at least somewhat uncomfortable. A combination of sit bone pain (I want to say that if feels like sitting on something very hard, but that's a poor description. I don't have any trouble sitting on, say, a stone bench, which is a lot harder. But I think you know what I'm talking about.) and perineal discomfort. The sit bone issues go away with softer saddles I've ridden, and the perineal discomfort seems to go away with saddles that have a groove along the middle. To me, this suggests a fairly soft saddle with a groove as optimal. Is this a correct assumption, or would I still be likely to be better off with a typical, fairly hard road saddle?

The WTB mountain bike saddle (well padded and with a groove) off my low-end MTB is the best I've tried on the S1 thus far, but 1) it leaves my MTB with no saddle and 2) I haven't ridden it further than a 60 km / 37 mile ride yet.
I'm currently borrowing a 'Selle Italia Flite Gel Flow' demo seat from my LBS. It feels too stiff, but I haven't ridden it at all far yet.

How far do I have to ride to determine whether a saddle really is comfortable or not? And how far should one expect to be able to ride comfortably with a well adjusted bicycle and a well chosen saddle? I rarely go far without stepping off the bike at all. There are always raisins to be purchased, water bottles to be refillled, photos to be taken, phone calls to answer, and so on and so forth.