The hardest students to teach were those who have had their heads in MSFS for eons, their lookout was non existent, they spend 85% of the time with their head in the cockpit, it should be 99% of the time out the cockpit.
That said, when I did my CPL many moons ago I found flight sim a great tool for learning checklists and procedures, I'd conduct a flight from A-B-C making sure I had the checks and briefs rolling off the tongue, for this it was great. Of course I could have done it in the armchair but it isn't as much fun.
When I did my IR I bought "Flying School", an add on which had a seneca. Again I used to fly routes with it to gain route knowledge and gain experience of what I expect to see on the needles etc. During the sim stage we had to do a STAR into BHX which I thought was quite complicated, I practiced this 4-5 times on FS and when I did it in the sim my instructor said he'd never seen it done so well, of course I didn't let on the secret, it wasn't because I was a good pilot, it was purely the practice.
Regarding VATSIM, I struggled when I was doing my PPL with R/T, I signed up with VATSIM and one day it all "clicked", it was as instant as that, so yes it did help.
Also before my IR test I used to get onto VATSIM and practice hold NDBs, Missed approaches etc etc at various airfields and it certainly helped.
Then came the sim assessment for the airlines, again I used flight sim to "do it to death", and it certainly helped.
As with all this Flight Sim didn't help with the flying aspect, because it cannot accurately model the flight dynamics, but it's a great procedural trainer for learning when to do checklists, and to get the checklists flowing off the tongue. Also for IR procedures.
Personally if you're a PPL student, keep away from it
