Well, Crawford is very valuable and will go in the first 8 or 9 rounds of any 12 team mixed league draft (provided there are at least a few managers who know what they're doing.)
Crede is a nice sleeper at 3B, but I think he may be slightly overrated around these parts. I could probably think of at least 10 3B I'd rather have.
ARod, Chavez, Rolen, Lowell, Glaus, Blalock, Tex, A. Ramirez, Ensberg, Cabrera, maybe Hinske and that's just off the top of my head.
Still, if it's late in the draft, and you still don't have a 3B, Crede is worth a look for sure.
Nix is intriguing, and maybe if I had just ONE more roster spot I'd pick him up, but unless you're in a really tough or deep mixed league or an AL only league, he probably isn't worth owning at this point. Right now, I have Vlad, Giles, Crawford, Kearns and Burnitz in my OF, and they all deserve a roster spot over Nix IMO.
If I get a DL exemption, Nix will be one of the first guys that will get a serious look from me.