Suspensions on turntable...really effective?

I don't know if suspensions are necessarily designed to reduce the impact of footfall.  The Linn simply sound better--lively and better bass--when the suspension is correctly tuned and the table is placed on an appropriate support surface.  

I have experienced all sorts of tables having problems with footfall so I don't know if certain types of suspensions are particularly vulnerable.  As a rough guess, I would say that light tables with suspensions, like the Linn and some JA Michell tables seem a bit more vulnerable to footfall.  I suspect that a much heavier suspended table, like my Basis Debut, is less prone to problems with foot traffic.

I have heard really nice systems with magnetically suspended tables (Gabriel and Verdier), but, I have no idea how to attribute the sound to the particular suspension; these tables also have in common the fact that they are extremely massive.   With both tables, I have only heard systems that were in rooms where footfall was not a problem so I don't have any idea whether they do a better or worse job in that area.  I also heard the MASSIVE ClearAudio Statement table (the most expensive table I have seen/heard), and it too has a suspension (both magnetic and a mechanical suspension); it was in a dealer system that was not my kind of system so I don't really know what the table is capable of doing.  

I haven't seen a clear correlation between suspended vs. non-suspended in terms of what sounds good.  Of the suspended tables I am quite familiar with, I like the Basis Debut (the table I own), the Gabriel, the Verdier, the three motor Audio Note table, and, I even liked a Linn LP-12 with a Naim ARO arm on it (completely different sound, but, appropriate in the particular system it was in (heard a direct comparison with a Basis 2500).  I liked many non-suspended tables, like the TW Acoustic and refurbished Thorens 164.  I would not rule any particular design out just on theory. 

Actually, magnetic suspensions on the tables I have seen are effective only in the vertical direction.  The platter is held in place by a spindle in a vertical bearing.  There is virtually NO movement permitted horizontally by that bearing.  The magnets support the platter only allowing for up and down motion.  If you press down on the platter it moves downward, but, the magnets act like a spring.  The farther the platter is displaced downward, the closer the magnets move and the greater the opposing force, and hence the force trying to restore the platter to the equilibrium position (like a spring).

The claim that Basis makes is that the suspension works both to isolate the plinth from structure-born vibration (i.e., from the outside and from the turntable motor) and to dissipate vibration created by the interaction of the stylus tracing the groove (primarily energy transmitted from the arm into the plinth).  The supposed downside is that decoupling the plinth from the motor introduces one additional element that may cause instability in the speed of the platter (Michael Fremer, the reviewer from Stereophile speculated, but never demonstrated, that the plinth could rock back and forth and this would change the platter speed).

 What I do know about my Basis Debut table (with the vacuum clamp) is that it does an amazing job of isolating the arm/cartridge from external vibration and at dissipating energy generated at the interface of the record and stylus.  If you place the stylus on a static record and hit the support surface that the turntable is on, very little gets played through the system (as heard at the speaker).  Also, if you tap the surface of the record itself close to the cartridge, the Basis tables also transmit far less energy to the cartridge than most table/arm combinations.  This translates into much less obtrusively loud ticks and pops; the energy of such sharp impulses is damped very quickly and effectively.  However, it is a matter of taste and system tuning as to whether such high damping of vibrational energy is desirable or not.

The Verdier tables are also in the highly damped camp.  The sound is "dark," and like the Basis tables, some might call it "dead" sounding.  I like the Verdier tables a lot.  Whether it is magnetic suspension, the extreme mass, the isolation of the motor by placing it on a completely different platform, or any number on other design factors, these tables sound good to me.