FWIW, a fellow lotus and I also have the ACT HDSS clutch and it chatters at low rpm crawl. I've naturally changed my driving behavior so that RPMs do not dip below 1k to avoid damaging my teeth and embarassment. The chatter gets a bit better after several hundred miles but doesn't seem to go away completely.
I have a stock flywheel and my friend had a lightened flywheel. My stock clutch worked great even with the VF2 supercharger. Ive not heard of anyone slipping the stock clutch w/ the VF2. The stock clutch is easier on the left calf, smoother, and cheaper. IMO, the HDSS is only necessary for 300+whp setups (TVS400, etc) or those who need to work out their left leg for one reason or another
I would have kept the stock clutch if I were to do it again. Too bad it's not an easy install. On a side note, I changed to the taller 6th gear from MWR and it made a great difference in sound and feel due to the ~500rpm drop on the highway. Gas mileage supposedly also improves by almost 1mpg highway, not to mention the higher top-end speed potential.
2006 Exige (Graphite Grey) - Hyper motorsports roll cage, 5pt harness, VFII supercharger, stage 2 exhaust, Larini decat, BWR street/track swaybar, BOE surge tank, gPan2, ACT HDSS, motor mount inserts, 0.715 6th gear, CL RC6/RC8 pads, sector111 steering arm, Quantum single adjustables, proalloy radiator, BOE/Fastworks level 2 full suite
JVC KD-AVX44 (rear-view camera), BTA6100 bazooka, polk audio front/rear, MTX Thunder 4-way amp, carbon fiber side scoops, LED strips (Audi style accent lights)