My teammate (youth player, 2nd Bundesliga/Austria) has been playing the Bluestar A1 on his forehand since the summer. Backhand with Bluestorm Pro. Since we train regularly, I have been able to gather impressions of the A1 in the last few months and also examine it myself and test it a bit on his blade (Boll ALC). Conclusion in advance: A very good rubber from Donic!
Compared to the Tibhar Hybrid K3, which I play on my forehand, the Bluestar A1 is similar: 52-53° sponge hardness, fine-pored sponge, very grippy top rubber. While the K3 is slightly (!) sticky when new - but loses this stickiness after a few hours of play - this is not the case with the Bluestar. The top rubber on the Bluestar is "only" highly grippy from the start (as is the case with the K3 after playing several times). The top rubber on the A1 gives me a slightly more compact impression than the K3. Nevertheless, despite the hard sponge, both rubbers have a relatively flexible top rubber, which allows for longer ball contact time and thus facilitates play over the table and active opening balls (especially against backspin). In topspin play, the Bluestar A1 seems a little faster and more catapulting than the K3. In my opinion, the flight curve is (even) higher with the A1 than with the K3. As with the K3, you have to be careful with the racket angle when doing topspin and blocking and close/close the angle a little more than with rubbers with a flatter flight curve so that the balls don't go over the table. Both the A1 and the K3 play well, especially when playing over the table, opening with a lot of rotation and when pulling back, because the top rubber grips the ball securely and the higher flight curve means the topspins make a nice, long curve. The weight (each in MAX) is a little higher with the A1 (~52-53g) than with the K3 (~49-50g).
Overall, due to these differences, the A1 has a little less "hybrid characteristics" than the K3 for me and is in return closer to rubbers with a normal top rubber and more catapult. In my opinion, both rubbers are optimal forehand rubbers for active table tennis at the table or from half distance, provided you can cope with the sponge hardness and can activate it. You should play spin block passively and move more actively over the balls. A1 and K3 are not suitable for "holding" or straight blocking. In contrast to the K3, the Bluestar has "identical" alternatives with a lower sponge hardness in the form of the A2 and A3, which I think is very good in this case, as the 52.5° sponge hardness is certainly perceived by many as too hard.
In terms of durability, I can say that the Bluestar, like the K3, also collects marks in the top rubber and gradually reduces the high grip. The durability is a little better than the K3, but unfortunately it is not very good either. As counterparts, the Donic Bluestorm Pro and Tibhar Quantum X Pro last about twice as long as the A1 or K3. After 60-70 hours of play, the loss of performance with the A1 is clearly noticeable because the high initial grip has reduced significantly.
Compared to the Tenergy 05, which was mentioned in the last posts, which I played myself for almost 10 years and still regularly stick on my brother's racket, the A1 is much harder and significantly faster when hitting the ball through. Due to the lower sponge hardness, I think the A2 or A3 are more obvious alternatives to medium-hard Tensor rubbers such as the T05. The jump from T05 to A1 is a big one due to the difference in sponge hardness (46° vs. 52.5°). I also have a training colleague who also plays in the 2nd Bundesliga, who tested the A1 in the summer and found it very good, but then went back to the T05, which he has been playing for over 10 years. He said the change would take longer for him and he feels less secure with many balls than with the T05. The playing and hitting feel is different with these new hybrid rubbers and takes some getting used to compared to normal Tensor rubbers or Tenergy. He is considering testing the A2 again in the future.
Overall, the A1 is a very good rubber. The only drawback in my opinion is actually the high price in combination with the durability. The same applies to the K3, which I have already written about in detail in its topic section. I have
attached a video (edited to ~15 minutes) from training a few weeks ago. Warm-up and 3 exercises. The material played is Ovtcharov ALC with Hybrid K3/Quantum X Pro or Boll ALC with Bluestar A1/Bluestorm Pro.