I purchased a 5870 a couple months back, shortly after their release - and, yes there was some bare-bones info on Eyefinity, but it didn't cover many of the details. (Likewise, the original drivers were pretty primitive.)
Since I hadn't budgeted any extra $$$ for new monitors at the time, working with more than the two old lcd's I already had wasn't a major concern. (Setting-up & oc'ing the new rig were enough to occupy my forebrain).
Now I'm checking into making eyefinity work and learning that the existing info on the net is contradictory and still not very clear.
Plus, since not that many pc monitors currently have native displayport connections (and I refuse to ever again give any business to Dell.... ever), my choices appear limited without the use of an adapter.
Spending $20 on a basic plug-in adapter is palatable, but dropping $100 for a simple adapter smells like raep.