I was tempted, but having read their T&C, I've decided against it.
They appear to be using the MMS network to push emails into the device and then charge MMS rates for each reply made. It sound like another 'revenue collector' to me, rather than a 'useful to the customer' improvement.
When I've got a device that can manage IMAP4 and web-based email such as Hotmail Live and Gmail - why bother to be charged 25p per reply via MMS?
Is there any technical reason Orange cannot use already proven push-email systems?