I think especially here in RG I haven't seen many aces but it seems very hard to return serves that are 220-230 somewhere.
The ace count is actually down on last year, but the first serve points won% is the same (well, down a little, but within margin of error).
My interpretation is faster airspeed, and little bit slower surface (ie more rackets on the ball, but not back into court, or not usefully so).
Serve speeds are slightly limited as a stat though, because they're measured too soon after contact. It would be more useful if they were measured just after the net - they'd be higher than last year at that point.