I have to agree that I'm not a fan of ads either. That said, I have one game that has ads in, and I've been fairly happy with the revenue.
The app's a chess game called Pocket Chess https://itunes.apple.com/gb/app/pocket-chess/id699609579?mt=8&ign-mpt=uo%3D4, which I released at the end of 2013. It has an AdMob banner at the bottom.
The figures aren't mind blowing, so I don't mind sharing them. In that time it's had 35,000 downloads, and made $1750 from ads. It took me around 3 weeks (full time) to create, so that's almost a satisfactory return on the time investment, still less than I earn from my day job though.
Revenue-wise, ads were a good choice for that app because it didn't take too long to create, there's a lot of downloads due to searches for 'chess', and I have never bothered to update it. Therefore I was able to make a ok return for the time I put in.
If your app is a little more involved, and you're taking a longer time to create it, then the chance of seeing a decent return for that time is far less. Very simple games, like the Ketchapp ones, are where ads make the most sense. Small upfront investment, lots of downloads.