I'm assuming you mean the bean bag type of mount that sits on the dash.
I own two of them and I couldn't be happier with my purchase.
They both were purchased from Amazon,one I paid 15.40 (U.S.) and the other about 17.50.
The price seems to fluctuate frequently. Whatever you do. don't buy a used one on Ebay. My friend bought one, paid over 21.00, it's quite worn and doesn't stay in place too well. It seems like the rubber padding on the bottom has deteriorated, perhaps by constant exposure to the sun.
I do put Arrmoral on my dashboard to protect from the sun, the surface is slick but my bean bag stay in place and doesn't move. I don't have a heavy foot, I seldom accelerate quickly so I can't answer your question on acceleration.
Normal driving should pose no problem and it remains in place regardless of the dashboard curvature.
I like them since they are a deterrent to car break ins. The glass mounts, if left on are a welcome sign for would be thieves.
Even if you remove the glass mount a ring remains on the glass that thieves look for. By using the bean bag, just hide it and remove the temptation. It's also easily moved to another vehicle should you need to.
Hope this helps you.