Suspensions on turntable...really effective?

Compare a Sota Jewel to a Sapphire.  They can sound almost identical.  However, the suspension in the Sapphire can definitely help if there is any movement at all.
However, a bad suspension is worse than no suspension at all.  I had a Thorens 125 with and SME arm and it was so bouncy that the hanging weight on the arm kept getting tangled...

I've used SOTA turntables (Sapphire Deluxe, then Cosmos IV) and have seen how they really isolated the playing from footfalls, etc. in a "medium" bouncy wooden floor setting.  I now have my Cosmos sitting on a Herzan active vibration cancelling base (yes, the type used to isolate scanning electron microscopes), and it just transforms the table into a much more neutral device and improves the detail retrieval.  The Minus K product mentioned above is also excellent for this.

+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.