Edit: CPM pays 1/3rd the rate, but CPC ads make up 90% of revenue, which makes sense if they generally pay more. I run a rather diverse set of sites, but I stay away from tech.
It may still be effective for pure consumer-oriented services, but is IMO useless nowadays for B2B unless you're a large, deep-pocketed company.
The frustrating thing is that if you do find keywords that have low prices, google will refuse to run them for you because too few people search for it. Citing "low quality", google will force you to artificially inflate your CPC just for the privilege of running a niche keyword.
There is this idea that every day there are X people on the web searching for exactly what you offer, and if you show them an ad during the search: success. I believe this to be true, but google makes it all but impossible to pursue low traffic, niche searches. They literally refuse to run them.