There are several high profile missing features in Lync. Many are ideas submitted in this very forum. There is very little evidence that Microsoft is paying any attention to this site, but we plug away nonetheless.
My idea is for Microsoft to actually do something about the missing features.
From my perspective, these missing features are the customers' biggest complaints.
Hold Music - why can't we just have server based hold music for every call either using media player or with a simple MOH port like everyone else. I know they say it's coming in CU7, but they said the same thing about CU6.
Call Pickup - No, I don't mean team call groups. I mean some mechanism, a short code even, to give the user the ability to pick up a ringing phone.
Call Recording - others have it and Microsoft could too. I know there are partner solutions but I hate bolt ons unless they are perfect.
Call Transfer - This should be really easy to do. All call transfers should be consult then transfer by default, but with the ability to just put the phone down to complete the transfer at any time. At the moment it is an absolute pain with Lync Phone edition. Requiring about 20 key presses. And communicator doesn't have this at all without making a new call and merging them together. Just awful!
Lync Phone Edition - just needs a redesign. Most things work well but many things are just too long winded. This is resulting in customers choosing to use other vendors PABX systems and either use Remote Call Control or Extension Mobility instead.
Attendant Console - The ability to use a phone would be good. I can't believe this is missing.
Response Group Out of Service - the ability for quick changes to response groups. IE Night Service or Out of service in the event of an evacuation.
These are the biggest pain areas I see. Feel free to jump on and add yours.