I have most of the NI drums stuff 50s,60s,70s, Drumlab, Studio Drummer and Battery 4 and although the samples sound fantastic played on their own I’ve found my Groove Agent 3 based songs mix easier and the drums sit better in the mix. I’ve had some cracking results with Groove Agent (the original) and GA3. I can’t say I’ve used GA4 much - more out of lack of time to learn it than anything else. In the same way I LOVE The Grand - I’ve got most of the NI piano samplers that are supposedly miles better but my old creaky (original) The Grand is my first choice piano - it cuts through like no other piano I’ve got - especially for bass reinforcement. I tried the Grand 3 and didn’t like it!
I do agree though that the new interface is a problem - when I want to get some basic drums down fast I still go to GA3. Steinberg are clearly trying to complete with NI Battery and forgot that some people actually like the old interface and when you’re tracking demos or sketching ideas GA 1-3 is superb.