There is a daily limit to the amount of items you can download, but in my experience it's quite generous.

I've encountered some problems on a few of the models I've downloaded though.  The first problems is in the way they are grouped.  Sometimes the object is one solid group so texturing different parts of it is impossible.

The other problem is that sometimes the objects, if they are multiple groups, import with parts moved, reversed, or missing.  It then becomes something of a challenge, sort of like putting a puzzle back together and figuring out what, if anything, got flipped, rotated, etc.