Quoted from ForceFlow:
It's good for trying out tables, learning rules, or playing tables that are too rare or expensive to get your hands on. Or for just playing while on the go.
This is spot on.
I've logged a few hundred hours on TPA (Steam w/Xbox 360 controller) because
1) I don't have means for the real thing yet
2) It's a very fun substitute.
At Pintastic I was able to play some of the real tables for the first time (SS , AFM , CFTBL).
I was quite surprised to find a fair amount of skills and shot knowledge translated nicely.
Knowing the rules so well definitely helped.
It's never going to replace the real thing but for people like me, who don't have a machine yet and can't get out to play more than a few times a year, it's awesome.
As a side note, I can also thank TPA for helping me get the Mrs. interested in pinball. Which in turn helps me get out to play the real thing more.
If anyone wants to add me I also go by Quint on The Pinball Arcade and Quint2525 on Steam.