Squeaked by on the switch exam with a 790 a few days ago. This was my 3rd time sitting for the exam after a few months studying.
Initially I used the Boson CCNP Network Simulator product materials for prep, but quickly learned that studying the actual Cisco documentation is the best preparation. If I had to do it again I would have bought used switches instead of using the Boson simulator product.
That said, I did use the Boson practice exam as well and I thought the questions were good and helpful with preparing - the material seemed better than the Network Simulator product.
If you've gotten discouraged and have already sat and failed the exam, don't give up.
Good luck and onto route!