Revup67 – I actually never have used the ISO1233 tool before, thanks for pointing out this useful comparison tool! I enjoyed taking a look at that flickr group, I think I’m leaning towards the 15-85 now… You mentioned the 100mm 2.8 L is also in your collection, do you have the tripod adapter and do you consider it necessary?
Personally, the ring adapter I feel is not necessary for this lens as it is rather lightweight though I carry around a 400mm prime frequently..maybe my arms are use to the weight of the 400mm so when the 100mm is on the 7D its like a feather. Mounting the camera body on the tripod with the 100mm and without the ring should be fine. If in need of a superb tripod head may I suggest the http://acratech.net/product.php?productid=76
Model GP-s which can fit nicely on a Benro Travel Angel or any standard tripod Boegn, etc. The GP-s head also acts as a Gimbal head. No plates come with this however so you can pick and choose. I got one for the 7D and 400mm. The plate for the 7D with the 100mm attached is plenty as would be for a 5D mkii. This head is rock solid - be sure to look at the instructional videos on this site. It's a chunk of change but there's nothing worse than watching a $4000 rig fall to the ground because of a crappy tripod / head. Luckily I caught my rig before it hit the sand. The cheap tripod was in the trash moments later.