Not in the least, if you post specifics that we, as food lovers, can identify with about why you had a great meal then it would be a valid review that anyone could use in determining the current status of that restaurant. If you just post, "we love the food and the service was good," it's a valid opinion but not much of a review. But if you've never experienced ANYTHING negative about recent WDW dining then ... Well, I just can't fathom that.
Well let's see...
March 2010: 4 girlfriends dining together. The service was a bit slower than I'd experienced but it worked out perfectly because the fireworks started just a minute or two after we left our table. (otherwise, we'd have had to wait) I had the goat cheese ravioli which I thought was off the last time I was there (Nov 2009), and it was very good this time. I don't recall the appetizers my friends had. I had the filet as my entree and it was great - cooked perfectly. One friend had a chicken dish that she said was good, but after trying the other's pork tenderloin, she said she wished she'd gotten that. I don't recall what the 4th friend had, but I think it was the pork. Two had the banana dessert and raved about it, I had the strawberry shortcake, which was good but lacked the "oomph" of some other desserts I've had there. Oh, we also had the cheese plate, which I was slightly bitter at having to share.
At the end of the meal, I pulled out my TIW card only to discover I'd brought my husband's old, expired one, not my newer one. I was so upset with myself - I even said I would get up right then and dash over to MK Guest Services to get a new one, but the server talked to the manager and they gave me the discount anyway. They didn't have to, but they did. (I got a replacement TIW card the next morning at Epcot. Actually no, I got a new one since it was just $25 more than a replacement and it extended my benefits another full year.)
June 2010 - DS (age 9) and I dined there. I had the cheese plate again (different selections, including one wonderful goat cheese from near my hometown in North Alabama!), the filet again and...now that I look at the pictures I realize I had the goat cheese ravioli again! Nearly the same meal. For dessert I had the chocolate lava cake with ice cream, but since I detest cherries, they did it with vanilla ice cream and a caramel sauce for the cake. DS had grilled cheese, which he was perfectly happy about, but I guess our server felt sorry for him because she brought him a dish of mac & cheese as well just as a little something extra (no charge). Of course, he doesn't eat that, but I tried it and it was good. Not as good as I can make at home or as good as what came with the filet at Jiko.
Note that if I ask DS where he wants to eat at WDW, CA Grill is always his first choice. He gets a grilled cheese pretty much everywhere, so it isn't the food. He just loves it there for some reason. Our servers have always been so kind to him, too.
This meal was in sharp contrast to the one we had 2 days earlier at Flying Fish. It was my first time dining there and I had the potato-wrapped snapper and thought it was flavorless. DS's grilled cheese was inedible - I thought he was just being picky or dramatic until I tried it myself. The service was terrible - we sat waiting for water refills or to have our needs met while our server continually played trivia with the table behind us. "Oh no, please continue the guessing game of 17 whatever-whatever characters with that table while I just suck on an ice cube to wash down this food."

The cheese board here was excellent, though - far better than anything else I ate there and I'd say as good if not better than any selection I'd had at WDW in some time. (V&A included)
August 2010 - me, DH, DS and MIL. Again, a terrific meal food-wise, but now that I am remembering each trip, I recall that our server was a bit off. I ordered grilled cheese for DS and he said they didn't have it.

I don't have pictures from this meal and I have little recollection other than I had the Yellowfin Tuna Three Ways (2 were excellent, 1 was not to my taste - a texture thing, I think - DH tasted it and thought it was excellent). I had the pork tenderloin for the first time in ages and it was as good as I remembered it from our honeymoon in 1998. I don't recall what I had for dessert - I think the lemon cheesecake. I have no idea what everyone else had except for DS who of course had the grilled cheese.
So I've definitely experienced poor food and service at signatures. I am guessing my Flying Fish experience is outside of the norm, but I'm in no rush to give it another chance, though one day I will. Citricos continues to provide solid dining and excellent service for us, as does Jiko. I've always had excellent service at Yachtsman Steakhouse, though the more I dine there, the more I notice that their menu is fairly limited. I was even pleasantly surprised with BD in August 2010 after not dining there in many years after a bad experience. It is THE best in-park dining if you leave Epcot out of the mix (and even then it might be the best - I suspect Bistro de Paris is better, but I've not dined there yet). Everything I had was very, very good.