Well hosting costs will probably go up a bit. That is one benefit to the current set up. I think I can get things running well for as little as $5/month (I think I pay $35 for 2 years of hosting now, so its more
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That is one consideration here... I like xenforo, it looks decent, but it costs $160. That might be worth it for having something stable and supported by other folks.
But again, if I roll our own, it does leave the door open for us to do other cool shit and build in a lot of custom behavior. One of the first things I'd want to do is integrate map views for each post for example, so you can "view current map" for each post and get a nice visualization