Jonolau...painfully, due to the universe conspiring to ruin my life, work has been just awful, and I've had very limited access to the courts and playing partners since the Aerogel arrived. Had a couple hits w/my family and a couple sets of doubles. So no opportunity to really wind it up on the singles court to give it a full workout, switching between it and the M-Fil to compare.
However, so far w/my limited court time, my feeling is:
1. The AG300 is stiffer and brings a bit more power than the MF300...not a huge change, I didn't have to mess w/my string setup to deal with it. No arm issues from the additional stiffness.
2. The AG300 feels more solid overall...a bit "thumpier" than the MF300, and does appear to handle off-center hits better
3. The AG300 is a bit more dampened than the MF300. Still works for touch shots and feel is still good.
4. The AG300 volleys better for me, getting better results in terms of solid, penetrating volleys, finess volleys still working very well.
Overall, if I had to make a decision which racquet to use in a tournament tomorrow, I'd take the Aerogel, I'm liking it more in most areas. But, if I had to switch back to the MF300 in the middle of the match, I wouldn't sweat it.
I think a lot of MF3 owners could try the AG3 and decide to stick w/the MF3 given the price differential. Whether the differences are worth paying twice as much (or more, depending on where the MF3 price settles) for the AG3 is going to vary greatly based on subjective reaction to the differences, disposable income, price sensitivity, and the always useful (to racquet companies) silly desire to own the latest and presumably greatest technology/paint job at whatever cost.
On note...my Aerogel arrived at 10.95oz/310g, that's actually a tiny bit heavier than the MF3 spec (309/10.9), and .2oz/5g heavier than the AG300 is supposed to be, so either specs were revised a bit, or I got one a bit on the high side of their manuf. tolerances. I was happy it was that way, and if I order another I'm going to request one as close to that weight as possible.