I think they can be used with analog signals too. After all, they are (I suppose) just a chain of transistors holding charge, like in a CCD. It is just the most efficient implementation, since doing it with logic gates will bring more overhead. EDIT: maybe not, it seems at least some of these chips have digital input/output stages. Maybe it could work if you put a very fast 8-bit ADC in front of the delay line, and used 8 delay lines, one for each bit? :)

Anyway, I have totally zero experience with these chips.

But I can imagine you clock-in the signal using a fast clock (maybe the internal clock), and then you clock-out the signal using a slow clock (slow enough for a subsequent ADC chip).

Also, perhaps you can put a bunch of these combinations in parallel to increase bandwidth, or to increase sample depth.