Yes, if you are serious about writing but haven't really made the big time or have a professional publisher who will take the place of a writers group.
Yes, if you want feedback from people who aren't your relatives and who aren't worried about whether they are being depicted in the work.
Yes, if you want to return the favor and read more of their work than they will read of yours (definitely a downside if you are crunched for time, although as an educator I am glad to do this).
Yes, if you respect the knowledge and taste of your group members.
Yes, if you can take criticism in a calm matter and not get huffy when someone states an honest opinion about what doesn't work for them.
In other words, yes, if you are an adult who wants to write better.
However, there are some downsides. I currently attend two groups and they are reading roughly the same portions of my WIP (new acronym I just learned). I get different opinions from them; one is a group of English professors (all graduate degrees) and the other "lay persons" who read a lot, write quite well, pay close attention to the manuscripts, and have gone to some serious workshops and seminars. The English instructors tend (myself included) to say "This reminds me of Kurt Vonnegut" or "This is like Flannery O'Connor." They are not as critical as the lay persons, probably because we work together and it would be best not to stir that pot.
The lay persons are far more critical, a culture we established in that group several years ago. Needless to say, the group has made some enemies because visitors will come who want us to say, "This is wonderful" and we just don't. We are honest. The first question I ask is, "What do you want to do with this piece of writing? Who or what is it for?" because I think those are the key questions. If it's for publication in the church newsletter, that's totally different from a situation where the writer wants a national platform.
One major problem I am currently having with my WIP, a sequel/novel/mystery that will eventually be 300 pages long (double-spaced) is that the groups only read 10-15 pages a session (monthly for the English profs, bi-weekly for the lay persons.) They, and I, just lose track of what's going on. I'm having that problem with a co-member who is writing a fascinating novel on a Cherokee community during and after the Civil War. She has a lot of characters and incorporates massive research, understandably, and it's just hard to keep up with them when I only read ten pages every two weeks.
I don't think this is a minor problem for those in long-form fiction. Short stories and poems probably lend themselves to writers' groups better