nostradamus is right, the downside of being a consultant is since you're not an employee of the company, you get no company benefits.
IMO it is a fallacy that this is really a downside. I spend a very small percentage of my income to pay for my own benefits. I have a PPO and can go to any doctor (in the "preferred provider network" is best but doesn't have to be) don't need referrals if, say, I wanted to go to the dermatologist I could just call them and it's covered. I regularly review my insurance costs and coverage and if I find a better plan I switch.
Companies want you to think that medical benefits, retirement, stock options, etc. are more valuable than they actually are. If you shop around you can save a lot. To me, stock options of a non-publicly traded co. are worth zilch. Savvy companies sometimes try to offer to pay me with stock. I always decline.
The benefits of consulting greatly outweigh the cost. If you like I can talk about these benefits more. The biggest caveat to consulting is finding the gigs and forming a network of repeat clients. Luckily I've been working in SD since graduating UCSD in 1993 and have a broad base of clients here. I'm lucky to have not sent out my resume or actively marketed myself in over 10 years but have worked non-stop whenever I wanted to. I get 2 or 3 calls per week that I need to turn down because I'm already on a contract.