Well I have the Sidekick and it is amazing; of course, the downside is T-mobile has a 5 year patent on this phone; so, if you don't have T-mobile service you cannot get one.
If you use it for business then you really ought to go and see the phones in person. The sidekick is great because the keyboard is functional - so many phone/PDA's are not functional for people who really need to use the PDA part of the phone.