I really enjoy contracting.
Here's how it breaks down:
Contract Perm
------------- ------------------------
2x pay Raises without asking (rate changes can be hard)
Paid overtime Vacation and sick days
Flexible hours 401k matching
More challenging Health care plans
Confidence building Less pressure to perform
Better IP rights More security (except in work-for-hire states)
My wife works perm, so we get benefits that way. (I used to get insurance myself... it cost a bit, but not even in the ballpark of the difference between contract and perm)
By "More challenging", I mean a few things. First, contracting forces you to at least occasionally make some effort to sell your skills. I'm not very outgoing... I won't pretend that's easy. However, I usually find it very rewarding (afterward). That's confidence building... I know perms who are scared to death of interviews. I almost enjoy them at this point. I'm very confident now. I absolutely know that would not be the case if I was perm. Projecting confidence is a significant part of being able to get what you're worth.
Next, I believe the technical challenges are greater, as usually a company is hiring contractors to do something relatively difficult and then leave.
As a contractor, I don't have to sign away every idea I ever come up with. Contracts should only cover IP for the project your working on. As a perm, virtually anything you come up with these days your company owns. This was actually a major consideration for me. For example: a friend of mine actually wrote a few chapters for an O'Reilly book, only to have her company block publication. People who come up with a great idea and quit to pursue it technically are stealing their own idea from their employer.
BTW - working full time for a company that turns around and contracts you to someone else is IMHO only good for experience building.