Right, I had a hard time figuring out exactly how long to put there time-wise. I think the amount of time you put in actually looking into what they're doing (figuring out what they're doing well, not well, their traction) can vary it quite a bit.
You're right about the pitch-killing. A few times I've seen investors pull out their iPad during a pitch and google potential competitors. Then they ask the entrepreneur about them if they weren't included.
I think it's fair though to spend 20-30 hours deeply analyzing the competition. What was their go-to market, their pricing structures, key focus, team size/background, economics, channels, partnerships, stated reasons for failing, what were they hiring for, etc. etc. Those all holistically give you a great view into lots of learning.
You're right about the pitch-killing. A few times I've seen investors pull out their iPad during a pitch and google potential competitors. Then they ask the entrepreneur about them if they weren't included.