I have my PA28-181 with Southern Aircraft Consultancy
I found their service to be excellent especially in light of the airplane being in New Jersey, SAC in Norfolk, me in Barbados and of course the FAA in OK City - they coordinated everything including my 'radio station licence' (don't forget that!)
All in all a painless experience - they even send out alerts for problems - got one last week giving a reminder/warning about the Olympic's exclusion zone - some poor guy wandered into it it would seem - not comething I am going to do but a nice bit of customer care and I am sure very timely and valuable to those flying in the region.
I did look at using other firms for my trust but response times were long - Faith at SAC responded immediately even though she was on holiday at time - the wonder that is the Blackberry I suspect.