Hi, well first this is not like the powerprep it is exactly like the current GMATPrep just with a different database of questions. One difference I noticed is about the scoring, in the first test I took I scored 750 - Q49,V41 but the same scoring - Q49,V41 - gave me in the real GMAT 730. Besides that the difficulty seems quite similar to the newer GMATPrep. Compared to the real GMAT, in my opnion the CR here is a bit easier and maybe some type of questions in the Quants of the real GMAT seemed really new to me, but they might have been pilot questions so I can't tell for sure.
Another thing here is a slight overlap with OG12, so some questions might look familiar.
Anyhow it is a great practice after you exhausted the newer GMATPrep like I did.