I don't use it. It really is becoming more and more difficult. Nowadays I can't get a reCaptcha right without refreshing it twice or thrice. Seems to me it's now a program to keep humans out as spammers (possibly bots) inexplicably still keep registering.
I'd still use it in a pinch. In practise though, using only a bunch of blacklists + eventual Q/A captcha seems to work just fine on keeping spam out for me whilst being far less of an inconvenience to users.