My experience has been almost all positive.
Devs love to give feedback. Devs have decent paying jobs, and therefore money to purchase devtools (ours is $79) Devs love trying out new things and being early adopters.
Why is it a terrible market?
-Less technically clueless than typical B2C or B2B customers.
-More likely to give feedback, helpful bug reports etc.
The negatives:
-Used to free stuff.
-Loads of competition (because every developers first thought is to sell to other developers)
-Relatively small market.
-The things @pydry said.
If there's an open source version thats half as good or they can hack together their own version with bits of string they will usually do that instead.