I've had great experiences over the years with Tek. I had a contract through them for a year about 8 years ago and then recently worked with them when it was time for a new position. They ended up not being my final selection but had a good experience with them regardless.
I will say they are way more legit than a lot of the "email recruiters" that appear to be popping up. You can actually visit their office and meet the staff. The recruiters are actually in town and follow up regularly...it's a company you can build a relationship and they actually work to find you your next role if you are a contractor. They are probably 4 stars as an overall company, but in the recruiting world they are certainly 5 compared to some of the bozos I've worked with.
Benefits-wise, I can't speak for current prices but we did use them for medical 8 years ago. It sure beat Cobra, but that market has changed so much I have no idea what it is now. But they are big enough that they offer a full online training catalog and actually are willing to invest in their contractors from a knowledge and career standpoint. My favorite recruiter, Trent, is no longer with them, but Sam was a great guy this time around and I'll certainly stay in touch with him for when this contract runs out. He is young, but he's very eager and really wants to do well.
My one tip to them is this: up the communication a bit. I was looking for a job during the holidays which is a HORRIBLE time to be searching (nobody wants to hire) and I didn't hear from them for a couple weeks. Which honestly is because of people's vacations and there being nothing out there. In fairness, I was in the middle of interviews for another hot lead and they knew that, so maybe they were waiting to see what happened. But a call every few days even if there's no update would go a long way to reduce the anxiety of job hunting.