Picked this up earlier and played one exhibition game so far: here's a screenshot of the post-match stats:
-I played it on Hard difficulty which is the 2nd highest. I was James Blake against CPU Andy Roddick.
-As far as aces, I was able to get 2 with James Blake, but only because I haven't really gotten the touch on the serving yet. Besides the aces, I did have several great serves that Roddick couldn't handle that ended up getting returned into the net or out of play by him. Andy's big serve had me in constant fear, I'm surprised he only had 6 aces. He had a countless number of serves I couldn't return. It seemed like the CPU took it's foot off the gas in the 3rd set and Andy didn't ramp up on his serves like he was. Maybe it had something to do with fatigue as I had him running all over as much as possible, or the CPU difficulty was giving me a break?
-The CPU and I each had a couple unforced errors in there, not sure how the numbers stack up to what some of you "sim-heads" are looking for, but they were there. My most played tennis game before this was Top Spin 2, and with regards to unforced errors I've found it's a lot harder to hit the ball out on a regular shot. In Top Spin 2 if you held to the left or right long enough with a top spin or slice shot it would almost always go out. That doesn't seem to be the case in TS4 from what I've seen. It's harder to be precise and work the lines which in turn makes it harder to hit it out accidentally on a shot that is easily returnable.
-The swing mechanic seems like the perfect hybrid of the "assisted" swing from Top Spin 2 and the "full-manual" swing from Top Spin 3. It rewards you for timing it perfectly like you had to in TS3 but within the risk of completely whiffing on your shot. As a semi-casual player of tennis games who enjoys realism, this really hits the sweet spot for me. Feels great. Your timing needs to be right hit precise shots.
-The game really shines with how they handled your ability to make tough shots. It pays more than ever to setup your shots and keep your opponent off-balance. You really need to work all of the different shots (top spin, slice, drop-shot and even lob occasionally) to force your opponent into mistakes. It's hard to describe not being a huge follower of the sport, but it seems to be handled in a more realistic way than ever before. Gone are the days where you can make a ton of miracle shots in a long volley, it's cool to hear the ball clang off the edge of the racket sometimes when it goes out, signifying you didn't get all of it. Little things that just add to the immersion.
All in all, seems like everything I wanted so far, plays like a dream. I'll play a few more games and post some more stats and impressions for yall.