I use On Top to do refresher work and find it helpful, but there are
some things I definitely don't like about it.
1. The Arrow power model has no relation to actual power settings in a
real Arrow.
2. The GPS is nearly useless. You have to put your own approach fixes
into the database, though it does remember them when you shut down.
3. The avionics panel has to be switched on and off. When it's on, it
covers the CDI. I rationalize this extra workload to compensate for
the fact that I'm not talking to ATC.

I do like the ability to "re-fly" the flight to review how well I did
holds and approaches.