I've never been involved in editing a Writers Group magazine / journal / anthology but I would imagine the hardest thing is to get the balance right. Some groups restrict submissions to members of the group, which is fine and particularly gives, shall we say, less established writers the opportunity to see their work in print. By doing this, it naturally follows that quality must suffer (harsh though it is to say it) - there is nothing wrong with this, it depends on the goals of the journal.
What I like about Boyne Berries, the literary organ of the Boyne Writers Group - and I've been fortunate enough to be included in a couple of its issues - is that it accepts work from anywhere, yet still has that local feel to it that humanises it. A poet from New Zealand sits nicely alongside a local prose writer from Trim and there is no diminution of quality. They must be doing something right anyway, because I see their name cropping up all over the place in poets' three line CVs!
To cut this short - and I could wax lyrical about the professionalism, friendliness and helpfulness of the group - Boyne Berries is currently open to submissions again from now until the end of July. Please read the guidelines carefully!