I have bought up a couple myself, but I am always weighing it against buying some bitcoin. Sometimes when I think of a really good domain name and then it turns out to be taken, I am kind of happy because I don't feel the pressure to buy it.
I bought
www.mtsig.com last week and I was pretty happy about that, I think as long as I use them for something they are worth it.
As somebody who invested six figures in domain names over the last decade: just buy bitcoins. The need for a great domain name (and thus the demand for them) is rapidly declining and will only get worse as the internet moves to mobile apps and platforms instead of individual websites. Ya if you could go back in time to 2008 and register a bunch of bitcoin related domains it'd be nice but short of that, people are just wasting their money.