Blackberry gone off
In general terms, I have to admit that mobile email makes my life considerably easier and used correctly it is a very powerful tool. Yes, there is the chance that the emails will look more like informal sms messages than the formal business email that we are used to but that is a user issue rather than a drawback of the technology.
As for the specific solutions, in my opinion Blackberry is past its sell by date, the Windows Mobile alternative has better devices and a much wider choice and an email solution that is at least as good as the RIM option. The infrastructure requirements for an Exchange house are easier and cheaper to deploy and maintain. RIM has realised far too late that even business users want attractive converged devices and are now desparately trying to tart up the range to try and compete with the Redmond mafia, too little too late.