I signed up with ThinkPost today. The service and support have both been outstanding. I had some problems getting my Pearl to sync up and Vincent spent around two hours of his Saturday helping me out - really cannot fault anything about the support I was given.
For somebody who has tried and failed to get several hosted exchange/BES options running smoothly, the service is a revelation. Entering tasks into Outlook and then a couple of clicks later having them show up on my Pearl is exactly what I have been looking for. For what it's worth (probably not much) this gets my highest possible reccommendation.