Oh boy could I write a book about this!
I belong to a women's distance group, all ages and paces. I will just list pros and cons.
Friendship, company on a long run, social events, finding new trails, safety in numbers, community service projects (they work with inner city kid track teams, pretty cool).
I almost ALWAYS ended up either running way under my pace or way over it on long runs. I seem to be in a no-man's land of about an 11 minute mile for long slow runs. The runners in my group are either Boston qualifiers who run a 8:30 to 9:00 minute long run pace (sure, their marathon pace is 8:00 minutes and under!), or sub-4 hour marathoners who run a 9:30 to 10 minute long run pace, OR, women who run a 12:30 to 14:00 minute pace, with a lot of walk breaks (some do far more walking than running).
I am convinced the few injuries I have had were either caused, or greatly aggravated, by this situation, because it seemed most weekends it was the 'fast group' going the long distance I am running, and by default I would end up with them.
So common sense says 'run your own pace!' Easier said than done when you are on an unfamiliar trail and don't want to get lost or be isolated. And, isn't that the point of the group, to run WITH people?
I have now backed away from my group for the most part.
It wasn't a good fit for me, but I love the women in the group, so it's been a hard decision!
"I just felt like running." Forrest Gump