No idea about the neuropsych test - I imagine it would be a lot more sophisticated than impact.

I did the impact test and found it reassuring in the sense that I scored pretty well, which made me more confident that my memory, reaction times, etc. were functioning at a reasonable level post-injury (although I did not have a baseline from prior to my injury, and I've always had a good memory and cognitive ability). However, while impact is helpful, it is a fairly basic 20-30 minute test. It doesn't tell the whole story, as Crosby more or less said recently, commenting that his passing a baseline concussion test (probably impact) was “encouraging, but it’s not everything.”