Brown Derby at HS
California Grill
Jiko
Artist Point - Very curious about the buffalo here
I am happy to give you our family's experiences at these places; I can tell you that every one is on our list for our upcoming trip, and that we've been to each restaurant several times in the past.
For us, the only upside to Brown Derby is that it's a nice meal within a theme park -- and that particular park (Hollywood Studios) does not, in our opinion, offer a lot of great dining choices. We use the deluxe dining plan, so it's not a hardship for us to give up the 2 dining credits it takes to eat here. So -- yes, the food is good, but it's definitely overpriced; but the benefit of being able to have a good meal within the park and not having to burn time going elsewhere balances it in favor of eating here.
We've had a range of experiences at California Grill, but we're going back this trip because we missed it last time around (although we'd opted to give it a break). The views from here are lovely -- even if you eat early, before the fireworks, the sunset is gorgeous (and they will let you back up onto one of their outdoor viewing platforms at fireworks time if you care to do that). We've had some of the best meals we've ever had at this restaurant, and then one that wasn't so spectacular (it wasn't bad, the food was fine -- but it wasn't what we were expecting for the price, etc.). I'd recommend anyone to try this place at least once. Like the other signature restaurants, the quality of your CM makes a big difference, but even "poor" service here has been (in our experience) better than good service elsewhere.
We love Jiko. It's refreshing to find a menu that's NOT a re-hash of other places on WDW property, the room is lovely, the wine list is fabulous (as is the one at Cal. Grill), and we've never had a bad meal here.
Artist Point is another one that's almost always on our list every trip -- the times we haven't gone it's only been because we so wanted to try someplace new that we were willing to give it a break. Haven't had the buffalo, but everything we've had here we've enjoyed. Also a nice wine list, and the meal/experience is enhanced when you have a knowledgeable CM.
All that said -- your mileage may vary, but -- as I said -- we're eating at all these places very shortly and are returning customers, for what that's worth!