I NEVER ever speak badly of my spouse when we're having problems, ever. I might inquire how someone else felt but I never tear him down in the process.
There's a very good reason for it, too. Chances are in your favor that you'll work the argument out with them and move on but whomever you've spilled the beans to might hold a grudge against your spouse, especially if it is a close friend or family member you've been talking to.
And of course if you are vehement about the depth of your anger and then it does get worked out, you could then be considered one who cries wolf.
I have a 'friend' that I frequently reject her calls as soon as I see it on the caller ID because I *KNOW* she's just going to tell me some sob story about how she picked a fight with her husband, slept with her boytoy, neglected her children and/or used drugs I don't condone the use of. If I do pick up the phone, I let her rant, I tell her to change it if that's what she wants and I get off the phone. I don't value her opinion, her parenting-style or really anything about her as a person at all because this is ALL she does in life. I certainly don't give a shit about anything related to her marriage. That's for sure!