Sustained Sequential Read up to (128k transfer): 500MB/s
Sustained Sequential Write up to (128k transfer): 130MB/s
Random Read up to (4k transfer): 62,000 IOPS
Random Write up to (4k transfer): 35,000 IOPS
They don't say what testing method was used though. Results with ATTO benchmark could be quite different. At least your sequential numbers look very close to spec.
I think that it is doing fine. HERE is some more data from Crucial.
Crucial said that they did their testing with "IO Meter", which is a free, open source program: IO METER.
You may want to give it a try, if you can figure out how to use it. I tried it using default settings and got unbelievably low results on my Samsung SSD. It is a complex program with a lot of different settings.