I think they are awesome. I get 8-10 sales from them a month. Treasuries, team etc, are where sellers hang out, not buyers.
When buyers are searching, the ads are what they see. My map cabinet knobs show up in maps, in jewelry and other categories. So, new buyers are exposed to them all the time.
Any advertising professional will tell you, it takes months of consistant advertising to see results. I spend a few dollars a week and get a lot of exposure.
I've never gotten a sale from a regular non FP treasury, facebook or a team.