I've been using/administering Exchange since Exchange 5.5 and just wanted to jump on top of the pile to voice my concerns as an enterprise customer.
1. The lack of support for Server 2012 R2 is disappointing. With the accelerated release cadences of Windows and Windows Server, Exchange should really run on the new version of the OS in a timely manner. Lync 2013 already has update out to support Server 2012 R2, and Lync is a fairly complicated product in my opinion.
2. The disappearance of the Edge role. As a customer, I liked having the choice to run anti-spam in my DMZ instead of going to Forefront/Exchange online. It seems as if the only way to do that now is to keep an Exchange 2010 Edge around or buy a 3rd party product? So I like using the Microsoft software but you guys are actually pushing me toward using a 3rd party for anti-spam.
3. Not 100% Exchange, but killing off Forefront for Exchange also sucks. You go from having an A/V solution which I could run on the Hub/Mailbox servers in 2010 that had multiple vendor A/V engines to the malware protection in Exchange 2013 which has one engine, not as many options and doesn't get as frequent definition files. Really?
4. The cloud / Office 365 should be marketed as Exchange for dummies. While I respect the cost advantages to the cloud, as someone who likes setting and maintaining Exchange on-prem and as a company, we're not ready to move to the cloud yet for email, so please continue to invest in, develop, and release on-prem features in a timely manner.
5. We, customers, all know that Exchange is really the only choice for enterprise email. I mean the google crap is just crap. So please bring back the quality we saw in the Exchange 2007 - 2010 era in Exchange 2013 and beyond. Don't leave behind the on-prem customers who have helped grow your product.