Pros
They are on the ball for onboarding people! 90% of their contracts are at Microsoft in almost every division. I have worked with and for several different vendor agencies and DLI is by far the best and easiest to work with. They have the process down to get your alias, RAS, laptop, etc. setup and going as fast as slow Microsoft can. Overall, this is a great agency to work for, especially if you are only looking for 1-2 years and/or to try out Microsoft. The networking opportunities are unbelievable. If you are just starting out, this is an invaluable place to learn and see what works best for you. Pay can be good, if you know what you are worth and you negotiate. Medical insurance for the employee are great (0 monthly cost to employee for medical and vision, dental is super cheap). They will pay for certifications and education, as well as business travel if your reporting manager wants it. They are very, very flexible at working arrangements, so you can work from home, telecommute, and work off hours as long as your contract manager is ok with it. They are also one of the few companies that have a managed service with MSFT, so the 18-month work limitation rule for MSFT can be avoided. (You can keep your job after 18-months and not lose building access) Most vendors from DLI are respected and treated well because the owners are both former MSFT employees. If you land a nice spot, you can easily work for them for several years.
Kontras
This list is unfortunately growing. Pay - if you don't know market rate, they will gouge/low ball you. Getting a raise is pulling teeth, so start high or you will have to beg every year. They don't automatically increase every year, you have to ask to get a raise. Vacation/sick leave is all PTO. you get 15 days because Microsoft made them give vendors 15 days. To save money, they took away the 401k. no retirement now. At all. Paid holidays are only the major ones (7 or so). As of today they do not match all of Microsoft's holidays, so you will be working on MLK and President's day while MSFT is closed. (As a comparison, MSFT starts you at 3 weeks vacation and 2 weeks sick) The Health Ins. is very good but the cost to add a spouse or kids is outrageous! Just to add a spouse it is somewhere in the neighborhood of $700 a month!! No stock (not public company), limited other perks. You are not their primary concern, the millions of dollars they make from Microsoft is. Transitioning to MSFT is very difficult and most vendors are treated as less than human. They will try to protect you and assist if you get cut thanks to a re-org or if the contract is done early, etc. but only to help them, not you.