I played the Ibanez BTB 7-string in a store for a few hours, and it was tuned with a high E string instead of a low F#.
Sound is a difficult thing to say just looking online. Which one's are you looking at? I actually liked the Ibanez a lot...it had the CAP pickups which are basically magnetic "blades" like the VFL's in Peavey's Cirrus line. It was pretty mellow, but had a really nice slap tone.
Obviously 7-string basses are big instruments so I had to get used to the neck, and it was a little heavier than I'm used to.
Hopefully you'll get a chance to try one out before you buy.
FunkStrat, there are quite a few companies now that do extra large string gauges just for drop-tuned players. Circle K, DR, D'Addario, LaBella all come to mind. I've seen .160 and .170 gauges!