Is the vpi prime a significant upgrade from the Scoutmaster.
I agree with you millercarbon. At first, it seems daunting, but adding the arm of one's choice to a motor unit is not that difficult when the deck is designed with arm options in mind. 
And Stingreen, once again we disagree. The mis-named second pivot (actually an outrigger on a crude skid plate) does little to push the unipivot to the sound quality level of a top gimbaled arm. I know from first-hand experience. 
My first serious table was a Thorens TD-125 Mk.2, and back then (in the early-mid 70's) no one bought one with the arm Thorens offered for it. I had an SME 3009 Mk.2 Improved mounted on mine, as did many others.
@fsonicsmith You know when a person starts a personal attack on the other it is usually to cover up statements that have no substance.

I have owned an SME tonearm on an ariston and my opinion is that the VPI unipivot betters it or the Ittok or about half a dozen other gimbal arms I have owned.  Again this is my OPINION just as your argument is no more than YOUR opinion.  Give us something besides an opinion.
Unipivot arms don't. They are a cheap and easy way to build a tonearm. No bearings to adjust no tolerances to meet. Too many degrees of freedom when you only want two. Even Graham has to resort to an array of magnets to stabilize his. A stiff arm tube is not good with a sloppy bearing. 
Atmasphere, IMHO I do not think speed stability is an issue with most modern turntables. I think isolation is significantly more important along with mechanical stability under the conditions that most of these units operate. Flash idea! As you know I am fond of suspended turntables like SOTA and SME. Why don't we engineer a turntable suspension that is tunable and can be modded for use with most unsuspended turntables. I do not know of an effective one and I am sure there has to be a patent in there somewhere.
VPI lost me with Unipivots, no anti skating, idler wheels and looks over performance. I do not want to spend money on jewelry. I want performance. Having said that they are coming around. Their new Direct drive table is handsome and you can get it with a gimbaled arm. Bravo. Now engineer it with an effective suspension, give it a dust cover and you are getting me interested.