ok, since Maxxc asked so nicely (:-)), I'll chime in with my two cents. Basically, yes...the FS688 and FS788 generally have the same character in terms of its general sound, but the FS788 does pretty much everything a bit better (more detail, more bass extension, more full-bodied sound, etc). One of my customers, a music professor for a college in Wisconsin, was going to use the FS688 as his reference monitor in a new recording studio until I played the FS788 for him (direct comparison)...and to him, there was no question that it clearly justified the higher price.
Suprisingly, even though the FS788 is rated only 1db higher in sensitivity, I've found that it is noticeably easier to drive than the FS688. With the FS688, you really need 80wpc or more to get something approaching the best sound from it...but I've driven the FS788 with a 50wpc integrated and it actually sounded better. Still, if given a choice, I'd use more power if possible.
Note that the break-in time on the FS788 is at least 75 hours...the amount of detail that you get before/after 75 hours is signfiicant; I guess the Scanspeak Revelator tweeter definitely needs it.
The FS788 will benefit from bi-wiring, but I also think that replacing the stock copper jumpers with something better can get you a long way there without spending on bi-wire cables (I use Audience Au24 jumpers on my FS788...I am also an Audience dealer).
FWIW, the Focus FS788 was the first Focus speaker I had ever heard...demoed them against a pair of Audio Physic Virgo II's when I was evaluating whether to become a dealer for them or not. To my ears, the FS788 made the choice easy...the Virgo II was doing something really special with acoustic music, but the FS788 being more credible and engaging overall on a much wider variety of music. I found that after getting the FS788, I was listening to my entire CD collection rather than just the acoustic stuff I was listening to with the Virgos...