Davenport is not that good. She has not reached a grand slam final for 3 and a half years. Her head-to-head with Dementieva is 3-4 (Dementieva leads) in their last 7 matches.
As many (John McEnroe in particular) have commented, Lindsey has powerful serve and return but her endurance is not good. The secret of beating her is to prolong every point. Don' t play fancy but just get the ball in. (In other words, don't try to "finish" Lindsay, but let her finish herself.) Karolina Sprem is a great player but got beaten badly by Lindsay twice, because her quick and flash style feeds to Lindsay's game.
Dementieva, on the other hand, has a good chance of beating Lindsay today. I say 50-50.