I'm pretty sure that both the Yoyo and Sigma clutches are just rebranded TSS units. The old ones were good but there have been some problems with many units from the past couple of years. I think there is a new design that hopefully addresses the problems.
I'm using the yoyodyne on my SV650 and am very happy with the unit. Makes me a lazy rider though. However, it is one less thing to have to think of under heavy braking and downshifting.
Ya, the clicking is normal. I had one of the newer (but not newest) Yoyo's in my SV and was getting slippage under acceleration. Took it out, put in the stocker and problem was solved. The problem is SV650 specific as far as I know.
I have the Yoyodyne slipper clutch in my 2000 SV650 and it has worked flawlessly for 2 years. The clicking went away after a full practice day and it actuates perfectly now. There have been some lubricating problems with some of the slipper clutches however (Steve can vouch for that). There is a lot of information on the SVRiders.com website about them. If you have a 99-02 SV you will need the 03 & up SV clutch springs (they are heavier). I got my Yoyodyne slipper clutch through Blair at SV Racing Parts, who is one of our track side vendors.