+1 on the Echo Puss on bass...I opened it up and messed with internal trimpots I shouldn't have touched, and now it gives me 750-800 ms of max delay time, and the feedback starts self-oscillating at a lower setting. Basically, I made it drop acid.
But the tone control is great for getting the most out of your top end and keeping the repeats clear, even as they degrade naturally. Or suppressing 'em for a Carbon Copy style dark wub..wub..wub.. cool in its own right. And for sustained sounds, the modulation is quite lush, and affects only the repeats.
Overall, I think the ultimate answer is that just about any delay pedal that sounds good on guitar will sound good on bass, taking into consideration the different registers.
With that said...one feature that would make the most sense, IMO, on a delay marketed for bass is a high-pass filter, preferably dialable, to generate repeats without mud while playing in the lower range. The Cathedral's Echo mode has something of the sort, the option to filter either low or high end progressively on successive repeats. I haven't actually messed with it much on bass yet, for which I have no excuse as the pedal is on the floor next to me as I type.
