As an example, I got one done for my (NOT YC) company (I ended up changing the name so I didn't end up using it). My experience was fantastic - the key is providing a ton of feedback.

The company was "Super Bomb Labs" the logo can be seen here:

http://www.superbomblabs.com/images/Topper.png

Hit the nail on the head for me with the combination of the bomb/vial and for $225 the price was dead on.

You can see the whole contest results here: http://99designs.com/logo-design/contests/logo-labs-7824

I know where the complaints come from but I have a hard time justifying paying 5-20x that price to get someone local to do it.