The Good:
Parts of the downtown area are pretty. It's trying to become a nice bedroom community for Portland, and it's kind of working.
There's an off-street multi-use path ("Springwater Corridor") that lets you bike west from Gresham all the way to the Willamette River on the far side of Portland, east to the town of Boring (which is aptly named and there's really no reason to go there, but it is a nice ride). At dusk, the part of the trail that passes through Gresham is full of tiny adorable bunnies.
Portland is reachable when you want it. There's even kind of public rail transit from one downtown to the other. It's a very long, slow trip that way -- not something you'd want to do if you had a car or a bike and strong legs. But if you have no car and want to get the kiddo to the Children's museum by train, you can do it.
There's a MMM community in the area with monthly potlucks.
The Bad:
The town has a reputation for being full of meth heads and petty crime. It didn't come from nowhere. I do think things are better than they used to be and continuing to improve, but it's not a non-issue.
Even though it looks close to Portland on a map, it doesn't feel close. Which could be a good or a bad thing depending on your taste for cities, I guess -- but the thing is, if you have friends in Portland, you will always or almost always be the one going to see them. They will not want to travel out to Gresham to see you.
Much of it is very auto-centric, big stroads and strip malls, etc. The sort of infrastructure that tries to force car clown behavior. You'll definitely want to spend some time getting to know the town before choosing a place to settle.