After the autoresponder runs out (6 days in my case) they've only got only a moderately higher chance of conversion than my average trial user. (~5% vs. 2.8%)
I really, really don't like the Put Up Fake AdWords Ad, See Who Gets Suckered minimum viable product. Aside from misleading customers and hurting the AdWords ecosystem (they don't actually get offered what they clicked to get offered, which Google will come down on you like a ton of bricks for if they detect, incidentally), it doesn't test your product. It tests your ability to write AdWords copy.
I could get 14% conversion to stabbing toothpicks under your fingernails, but what does that tell you? The world has weird people in it, and I'm good at qualifying non-weird people out with my ad text and keyword selection? Whee?
Similarly, if I delivered an AdWords campaign that was awful (low CTRs, low conversions), would that tell you the product is awful? Because I've done that before, too -- the first draft of my AdWords campaign for Bingo Card Creator was terrible. It took me almost a year before I figured out how to write AdWords decently. That was not an indication that the product was terrible (I sell it quite successfully), it was just an indication that I needed to adjust to a new way of copywriting.
If it can't tell you if an idea is good, and you can't trust it if it says the idea is bad -- what is the point, again?