One thing you may want to consider is wether you want to get email delivered or be able to collect email.
A subtle difference, but being able to choose when you collect your email can be quite relaxing. I check my email very regulalry when on the move, e.g. as soon as I finish a meeting, on trains etc. but unlike "crackberry"
users do not get my mail pushed at me - I use IM, SMS and Voicemail to SMS in meetings if I MUST be contacted with abit of information.
It seems in some organisations that because they know their Blackberry users get email almost instantly the response should be instant. Fine if the work really demands that but intrusive when it interupts meetings with stuff that could or should wait.
I'd think about your company culture and your work style before choosing.