I saw this on GrubGrade and was intrigued, so I went to Wendy's last night to try it out. The quickest way to describe this thing is that it's a double cheeseburger with Wendy's "secret sauce" on it.
In a word, unimpressed. The sauce didn't add much to the burger, despite there being a good amount of it on there, and the rest of the ingredients are on any other one at Wendy's. For $2.99 for the sandwich alone, I expected more. Something fairly unique, and something I'd try more than once... but there's nothing about this cheeseburger that's different from a single or a double, because like I said, the sauce is pointless. It's not terrible, but it's certainly "been there, done that."