Suspensions on turntable...really effective?

+1 for Sounds of Silence. A Vibraplane will make a positive difference in any system. Alternatives are Minus K, or at a much higher price Herzan.

Steve at Sounds of Silence is great to deal with.

I use a "vintage" Linn Basik (Akito) with no suspension to speak of except the large rubber hollow feet it sits on (the turntable is on a light but stable little table of its own, as per the Linn instructions!). I recently obtained a second REL sub and it's about 4 feet from the turntable, all on a classic potentially bouncy wood floor. The result is zero footfall disturbance, when I touch the side of the turntable when blasting something no vibration is getting through (at least that I can feel by touch)…and the damn table sounds great and plays beautifully. I keep threatening to replace this table but it works so well I can't get rid of it.

I think the issue is, really effective against what? For example, a Linn, although spring-mounted, is terrible with footfalls, while a Basis, also spring mounted, is much better.  There are many theories as to how to design a tt.  Some say that spring-mounted tables are always in a state of oscillation and that a heavy plinth is the way to go.  So the short answer is - I don't think you can generalize about these things.  Each table has to be judged for its own merits and you shouldn't be shopping for a tt based on whether it is suspended or not.  There are just too many factors that contribute to the sound.   

Well, it's pretty obvious the springs for the Linn are the wrong springs.  Because if they were the right springs the turntable would not be affected by footfalls.  There is a very simple relationship between resonant frequency, mass and spring rate. Most likely the folks at Linn didn't get the memo.