I've driven a number of step cars and found them nothing but frustrating. The only automatic I've ever driven that I don't find thoroughly frustrating is the S55 AMG. And that's mostly because it has massive torque reserves that sort of make up for it.
Have you ever driven a car with a CDV? I probably am one of the better qualified here to comment on that... Shifting speed was hardly affected at all by removing the CDV. The only place it makes any difference is off the line and in "power-shifting." Off the line, I can launch marginally harder than I could before I removed my CDV. Powershifts grab very slightly more quickly. However, with decent driving technique, a CDV will not affect performance substantially. The CDV impacts driver FEEL, which is a totally different ballpark. If feel impacted performance so much, the E46 would be dog slow.
The key with stick launches is to do them properly. A stick can be incredibly slow off the line if launched wrong. Drive a WRX if you want a truly dramatic example of this. Plenty of people screw up launches, plenty of people also take them easily. Driving very gently in a stick will probably be slower than with a slushbox. Properly driving fast, however...
That said, SMG II is AWESOME for track drivers. IMHO, there's no question on this one. My left leg gets sore if I don't use it, though, so the left pedal is a necessity as far as I'm concerned.
2006 GMC Sierra 2500HD 4WD Duramax LBZ/Allison 6-speed
2002 BMW M3 Alpinweiß/Black
1999 323i KP/GTS2 Alpinweiß
1990 325is Brilliantrot/Tan
1989 325is S50B30US Alpinweiß/Black
1989 M3 Alpinweiß/Black S50B32 (321hp, ITBs)