I'm not going to comment on whether or not Aerospike is ACID, I have no idea, but I can give a bit of info on CAS vs ACID.
CaS (Compare and Swap, or Compare and Set; they're almost identical, and don't really have a clear distinction) is the process of validating a record's value before performing an update. This helps a lot with Consistency (the C in ACID), but doesn't guarantee the other three (Atomicity, Isolation, and Durability).
Aerospike might have systems in place to address all of ACID, but if they're claiming CaS is ACID then they're just lying.
CaS (Compare and Swap, or Compare and Set; they're almost identical, and don't really have a clear distinction) is the process of validating a record's value before performing an update. This helps a lot with Consistency (the C in ACID), but doesn't guarantee the other three (Atomicity, Isolation, and Durability).
Aerospike might have systems in place to address all of ACID, but if they're claiming CaS is ACID then they're just lying.
Look at the Wiki page on ACID ( http://en.wikipedia.org/wiki/ACID ), it's actually pretty good.