I'll preface this by saying I took 13-14 years out (didn't pick up a racquet once) and have had 6 or 7 hitting sessions only in the last 3 weeks, and hadn't played poly since a couple of abortive attempts with Alu Power / Big Banger nearly 20 years ago.
Stringbed felt DEAD. No feel whatsoever. I understand why some people are complaining about snapback, or lackthereof .. snap is probably the wrong word - springback. There's nothing snappy about it. I feel like this property is also part of why pocketing feels excessive (which it really does on the forehand). It made my shoulder hurt on the forehand fairly quickly - pretty much zero vibration or feedback but pocketing was so long on bigger cuts that there's a significant delayed shock. OHBH drive and bunts felt awful. It felt like the racquet had lost all torsional stability and power and sweetspot was a lot smaller. The pocketing was much less extreme than the forehand, but still interfered, especially when trying to hit hard with a big follow through. Short crosscourt it helped obviously. Launch angle was extremely low (even playing on a Gravity Tour '25) on forehand and low on backhand. Slice backhand was probably the lone positive, the combination of pocketing and shaped poly REALLY knifed the ball. Volleys were total ass feel wise, but slices were good, and drop volleys easy due to pocketing. Didn't serve, but I guess kick and slice would work well due to pocketing and shape, power would suck and feel would be bad and shoulder shock off the charts bad.
It was a windy, damp evening, and I will try in better conditions, but switching to a Prince Graphite II 97 with TF X1 Bi (17G 56/54) I had none of the issues that I did with the Head GT '25 with HM (also previously strung with X1 Bi). I had the HM at 50/48 and 17G. GT was originally strung with X1 Bi 17G at 52/50 (too low) and probably finished at about 40lbs (wayyyyyy too low, but still felt much better than Hypermach). With the Prince / X1 Bi I got much more pace, higher launch angle (despite being a lower l.a. racquet than the GT) no excessive pocketing and deadness (which I initially thought could be due to damp heavy balls).
I realize I'm going from the creme de la creme of multi (Gamma Live Wire Pro maybe the only better) to a very divisive poly / poly hybrid ... but this really felt like garbage.