The last couple of times I was at my local Wendy's, I've noticed that they now sell fish - kinda creepy, but I was also kind of intrigued. I don't know why, but I insisted on trying it last night. The first thing I noticed when I peeled away the wrapper was just how much sauce they had put on it, it oozed over the side of the bun and dripped onto the inside of the wrapper. I got a huge gob of it in my mouth with every bite, my inintial thought were "Um, is that butter. What is that taste, and why is there so much sauce?"
I do know that the tartar sauce was a little overpowering and tasted like butter that had gone bad, not great. The fish part seemed ok - it was surprisingly crispy and fresh-tasting, but it was so hard to tell under that much sauce, so if I ever got it again, I'd opt for it without the sauce.
I'm not a big sauce person, usually I get my burgers sans ketchup, etc. so if you love mayo, this might be right up your alley.