It is when you have to stop down that a lens with a great VC system like makes a lot of sense.
Interesting review, thanks. One question though since i see you've also got the 24-105L with IS (next to a zoo of other lenses in this focal range): Do you think the f2.8 aperture makes a decisive difference for your work, and when do you still use the 24-105L at all if you are so convinced by the Tamron?
The limitations of speed on the 24-105 is one of the main reasons that I got the Tamron. I didn't often use it for event works, choosing to use mostly primes for the speed. I found that I was sometimes limited in framing on wider shots or stuck without time to change lenses. The Tamron has fit that bill well. I dropped my 50 f/1.4 and 35 f/2 in exchange for the Tamron. It serves well enough for narrow depth of field shots that I don't miss the speed of the primes at that focal length (particularly when you can zoom into 70mm for that extra bit of compression). The VC enables me to keep ISO and shutter speed lower when shooting static shots (it is pretty amazing for this, particularly compared to the primes). The faster speed of primes is not helpful in this situation because you frequently have to stop down to enlarge the depth of field.
At the moment, I do still have the 24-105L, but primarily use it when travelling for the extra bit of reach. I will probably sell it to help purchase a lens or body that I feel will serve me more in the future. I don't often use it in an event setting (although you could, particularly if capturing static subjects or cranking ISO). My primary reason for not moving it sooner is that I have been extensively testing the Tamron before making the decision and my filter selection in 82mm threads is limited. Even my Cokin P system vignettes pretty badly until close to 30+mm zoom. I still would like to get a decent ND filter (I have only UV and CPL at the moment).