I used Abbott Printing consistently for about a year and a half at my old job as a communications coordinator for a medium sized nonprofit.
We used Abbott's services for jobs ranging from relatively simple to more complicated. Their prices are very competitive, and they were able to handle some more tricky work - like a large company brochure with special inks and diecuts - with no problem.
Todd Knowles is the rep I worked with directly, and he was extremely helpful and friendly. One time there was a mixup that resulted in our office having to stuff about a thousand envelopes by hand, and Todd came over to help personally.