I got my complete G&P bolt today 1 hour before leaving for my CQB game and so was able to test it. As @AlphaBear mentioned before, the machining is of very high quality. The screw with the C-clip also sits around 1mm away from the bolt instead of flush, so I reckon this is some kind of design decision.
Initial thoughts are that it is indeed completely drop-in unlike the Angrygun bolt was for me (dodgy sealing buffer meant shitty firing rate and sticky nozzle). I got a 0.30J increase in power which was unexpected and not entirely welcome since I originally intended to use this bolt for my CQB arena and install the G&P adjustable valve in my stock bolt to use outdoors as a DMR, but it seems like I'll have to figure something else out. I only tested with 0.25g bb's, but I was consistently getting between 98 and 101 m/s, so around 1.28 and 1.32 joules. It was very consistent , I would get 101-102 m/s with a fully filled mag with green gas, and after 10-15 shots, it would settle to around 98-99m/s. Also, I noticed a distinct change in how the gun sounds when firing. I'm pretty sure this bolt is louder the stock MTR bolt, and it has a distinct metallic sound when firing which is really satisfying which the Angrygun bolt definitely didn't have. I wonder if this is due to the roller bolt design?
Overall, I'm pretty happy with how it turned out! I'm glad that it worked OOTB and didn't require any fitting or anything. Also interesting to note, the G&P bolt didn't engage my hop up dial like the Angrygun one did (the AG bolt would literally decrease my hop from 60% to 0% in a magazine or two), so I'm staying well away from AG internals for the MWS to be honest.