There are 2700maH capacity batteries by Powerrex/Maha (same company, different trading names). As far as I know they won't outperform any other major brand 2700maH batteries.
What you might have heard of are the Sanyo Enloop batteries that have become very popular - however its important to note that many of these are not large in capacity and are often less than the max on the market ( though I think some new larger capacity ones might be on the market now). The attraction to these is not the capacity or recycle rate, but the fact that they will hold up to 80% of their charge after around a year without use. This is fantastic for those who don't have a planned shoot and want to be able to leave the batteries in teh flash and still have them usable when they go to use the flash - and in this respect the Enloops are fantastic. I had a set of 4 batteries in christmass and 2 months later used the flash without any problems - regular rechargables would have drained down considerably over that period of time.
You might want to look at external battery packs if you want faster recycling and more shots - they would certainly give you both advantages that you are after if you are willing to put up with the added bulk to carry.
Also remember that a rechargable battery is only as good as the charging unit that you use - a good recharger is essential to ensure a good long usable life of the battery, the quick (and cheap) 30min kind of chargers are no good long term and will dramatically cut the life and storage capacity of batteries recharged in them - esp things like flash batteries that go through a lot of recharging cycles. Spending good money on something like a Powerrex/Maha recharger (C9000 was what I went for myself) is well worth it long term.
Tools of the trade: Canon 400D, Canon 7D, Canon 70-200mm f2.8 IS L M2, Sigma 120-300mm f2.8 OS, Canon MPE 65mm f2.8 macro, Sigma 150mm f2.8 macro, Tamron 24-70mm f2.4, Sigma 70mm f2.8 macro, Sigma 8-16mm f4.5-5.6, Raynox DCR 250, loads of teleconverters and a flashy thingy too
My flickr