Blackberries work the most flawless with it, I havent tried an Iphone which I am sure works flawless as well.
Any recent blackberry will give you full synchronisation of contacts.
I have connected many different phones and many do work as well, but with many others I have had problems with contacts that had multiple numbers, BT picked one and never imported any info about other number.
With Blackberry it imported all unique numbers and if you had the same number twice for your contact it ignored the info.