I don't know why they're so popular. They suck (pun intended). I've been given plenty and they ranged from outright terrifying (too much teeth!) to just kinda meh. I'd rather get a handy than a BJ.
I'd rather just fuck, forget about the BJ/HJ. If she wants to be eaten out, no problem I'm down. But personally, I have no interest in the appetizer, give me the main course. It doesn't do it for me.
But I've been with my first girlfriend for 10 years so I might not have enough experience to make an informed decision.