I tend to only buy dotCOM, as that's what the general public is most comfortable with. I've found that if you buy any gTLD, you immediately create a headwind that you're fighting against out of the gate..
I refuse to buy domain names from speculators. I think it's one of the scummyest (legal) things you can in relation to the internet. You're buying cheap resources on the hope that someone is desperate enough to give you more money for it later. They're middle men that provide no service and add zero value to the world. They're just selfish.
I mean to say that I buy domains from auction when an original owner abandons a domain.
And don't be so put off from buying a domain from a speculator or broker.. If someone owned a piece of mountain-view property, would you consider them scummy? There was no guarantee these domains would appreciate in price.. These domain investors took a huge risk in the early days. And it happened to pay off for them.