I played around with an aluminum-handled AUS 8 M21 (the hollow-ground, recurved M16) for about a month before I decided to sell it. I would describe it as very decent for the money. Nothing objective here, just going to describe it as I saw it.
Blade: very utilitarian. The hollow grind brings the edge quite thin, and therefore performed quite well as a cutter. The recurve was very subtle, so I doubt it made a difference in anything. AUS 8, as usual, can be brought to a hair-popping razor edge due to its edge stability. The almost-full-length thick spine strengthens the tip greatly. It easily holds through batoning, and the strong satin finish on the blade refused to be scratched or marked.
Handle: I was blown away by the high-grade aluminum. Not having handled any high-grade aluminum before, I was initially expecting pots & pans aluminum. I could not be more wrong. The 6000-series aluminum, as a heat-treatable aluminum, was strong and heavy. I was not able to casually scratch the satin finish on the handles, even with the blade when disassembled, and you wouldn't be able to distinguish it from stainless steel at a cursory inspection.
I was not impressed by the design of the handle, however. The handle has 4 holes on each side to skeletonize and lighten them, but they provided great places for lint to enter. Also bad was that the two-piece separate scales were screwed together with spacers only. This means the blade was sandwiched in the hollow space between the two scales. The spine of the blade blocks off one side of the length of the "sandwich", but the other end, containing the sharp edge, is wide-open. No part of your hand will ever fit in the slot, so it is safe, but it did allow coins and paper to get between the scales and get cut by the blade/ruin the edge on the blade. I learned not to carry any loose objects in the pocket of the knife.
I also did not like the untextured nature of the scales. Aside from the satin finish, the aluminum handles had no features to prevent slipping. This was the (very personal) reason for me to sell the knife. Many other people consider this not to be too big of a deal.
Lock: Lockup was solid, no play in any direction. The knife was easily disassembled by two torx screws and a slotted pivot screw (DO NOT LOSE THE O-RING UNDER PIVOT SCREW!), and teflon-impregnated bushings space either side of the blade. No problems were observed with the opening action even when lint tried to interfere. The liner geometry was well-designed (for me), and it was impossible (for me) to disengage the liner lock even in a twisting deathgrip (my hands don't have much meat on them, though), but it was easily moved by the thumb. The 420J2 liner (only one liner) had a remarkable finish on it that I've never encountered before, that gave it great traction wet or dry. Which was moot point, because you never touched much of the liner anyway, and this is the finish they really should have used on the scales.
Lock showed no movement, and the knife passed the slow-open-and-push-spine-test and a moderate spine whack. The lock was also solid under batoning, however it did develop play. This was later fixed by adjusting the pivot screw.
Overall: My only personal beef was the slipperiness of the handle scales, which due to the finish managed to be slippery dry or wet
. Your fingers sort of just glide on the surface of the handle finish; in fact it would have given you more traction if they just made the handles smooth due to increased surface area your fingerprint touches. If you don't mind that, the M16/21 and Spyderco Delica are probably the best deals in folders in the $30-$50 range.
