I've worked for a Managed Services Provider in the past and I can say that outsourcing your IT works well for companies with 100 employees or less who are basically centralized in one or two locations. Any larger employee base than that or multiple locations tends to pose logistical problems. MSP's (especially smaller ones) have difficulty servicing remote locations. Most times they are forced to contract out to freelance IT people and you never know who will show up at your doorstep to help "fix" your IT issues.