Groupwise as an Admin is a great product. As an Admin I have no doubt which email system I want to administer. Other than the lack of eDir integration in the last 15 years is perplexing, but I do like that my users can have these massive mailboxes and it is secure from end to end.
But that has been that way since at least GW 5.5. The client interface was good at GW 7 and it is stable unlike the GW 8 client. I didn't need a rewrite of the Client just to make things seem pretty. I need real world features that matter to the user such as GMS, QUICK message level restore, and simple, powerful and easy integration points for 3rd party vendors. Heck, copy the integration point of exchange so that 3rd party vendors can write one product that works with both systems. I know this means that you will have to work to keep your APIs in lock step with Exchange but you know the saying: "Lead, Follow, or Get out of the way". You have lost almost all 3rd party support, it is time to get it back.