I'm not sure if I've seen any benchmarks of it, but I have quite a bit of first hand experience with hercules GF2 Ti card.
First I should correct a few things though, it runs at 250/200 by default which is exactly the same as nVidia's specifications for the GF2 Ti chipset.
It does however use 4ns DDR SDRAM which in theory is rated for 250MHz DDR operation, so while theoretically it should be able to clock to 250/250 it does not default as said speed.
The GF2 Ultra's default clockspeed is 250/230.
As you said, the GF2 core is primarily memory bandwidth limited so every last bit of bandwidth can have a significant impact upon performance.
My comments upon Hercules card in particular: It's well built and should be quite reliable but that's to be expected from the well reputed Gullemot/Hercules. It comes stock with TV-Out which may be useful to some. It has decent though not great GPU cooling, and comes with ramsinks which should potentially aid in memory overclocking, as stated above it also has 4ns DDR SDRAM which in theory should aid in overclocking considerably.
One slight downfall to the card is that the 2D image quality is somewhat disappointing. While it's not terribly bad, it does fall prey to nVidia's somewhat poor reputation in that regard. Still, the 2D is more then adequate unless your looking to run at resolutions of 1280x1024 or above in which case you might be better off passing on Hercules card.
The largest downfall to the card IMHO is that despite the 4ns DDR SDRAM used which should in theory allow it to be an excellent overclocker, the GF2 TI from Hercules seems to be among the worst overclocking Ti's. Be it that their not supplying enough voltage to the RAM or they've simply chosen some rather sub-par 4ns RAM I can't say.... but having tested 3 GF2 Ti's from Hercules, even the best of them managed a somewhat disppointing 230MHz memory clock. My experiences seem to be the common trend, as the vast majority of posters on Hercules own message board have expressed significant disappointment with the card as despite it's 4ns RAM very few boards seem able to clock to even 230MHz memory clock.
Given that the board is priced slightly higher then most other GF2 Ti's, I find it hard to recommend if your looking for a Ti that will overclock well.
There are a few other boards that have displayed consistently better overclocking resoluts for a lower or competitive price so I'd personally pass on Hercules model.