Ask HN: Practical differences between B2C and B2B

Title says it. I'm interested particularly in how to launch. With previous b2c stuff I've done, I launched as soon as I had something that didn't break constantly. It still broke often, but it would be usable and thus testable. I'm now researching for a b2b idea I have. Should I have a more complete product to start with before drumming up clients. Will businesses lose interest more quickly if they see 500's occasionally. Or if the feature set seems slim at first?