Lazyturtle, I just bought a pair to replace my scubapro jetfins for blue water diving...
I was looking for a lightweight "power" travel fin (that plus I can't stand the foot pockets in jetfins!) and ended up with the Quattro Excels. They seemed to be the stiffest of the paddle fins at my LDS. A bit pricey though...
I had a chance to use them for 10 dives over the long Easter weekend and so far I give them a big thumbs up. Didn't take too long for me to get accustomed to them. I dive mainly tropical waters with a 3mm wetsuit so the lighter weighing Excels weren't a problem. I can only compare these to my jetfins and Tusa imprex triex (used for a brief time). The foot pocket is nice and deep and encloses most of my foot. I've noticed less strain on my calves. I've got tree trunks for legs so I didn't find them as tiring as some online reviews have mentioned.
I swim mainly with a frogkick and the Quattro Excels worked like a charm. Seemed like I would get more mileage out each kick compared to my jetfins. They also worked great in against a stiff current (much better than my old jetfins IMHO). We dove a corner site with a ripping current where we came up against a shoal of barracudas sitting out in the blue just off the point. The Quattro Excels really made it easy to swim against the current towards the barracudas and allowed me to hold my ground while I took some photos.
But even without a current, these fins are great. It just seemed like I would get more distance out of each frogkick compared to my jetfins.
They are pretty long fins and it takes a little bit to get used to manouvering with them but after awhile I didn't have problems doing helicopter turns, back finning, and other fine tuning strokes while shooting some pretty small macro stuff.
edit: oops, I didn't realize the AVANTI Excel are the full foot version. The above comments are on the same design but open-foot Quattro Excels. I would image the fullfoot design would make them even better!