Outdoors -- pretty beautiful really. Great whitewater on the Payette. Longest stretch of continuous runable class 5 anywhere in the states, I think. Best part about Boise outdoors is it's not that crowded. You can go into the lesser known ranges in the state and not see anyone for days. Fun and easy to travel in the backcountry because the vegetation is sparse and there are no glaciers. (I guess I miss glaciers sometimes, and if you like super thick forests, you might not like the sparse vegetation). You don't have to drive anywhere to go for a run in the foothils. You can get up above the city in about a 20 mins running from the north end. Skiing is 16 miles away. There are some close climbing areas (within 15-20 mins) and Asana
http://www.asanaclimbing.com/home.htm is a Boise company and they do a lot of climbing stuff in the community, so climbing culture can't be too bad (I only just started climbing so don't know much about it)
What's impressive is you have all this stuff that's relatively uncrowded in this city with a great downtown and surrounding neighborhoods. I've had friends visit from Bellingham and the Bay area who both LOVE the downtown... and all it's beer.
http://www.justeatlocal.com/bittercreek has one of the best beer selections I have ever seen. Ok, compared to Portland, no where has great beer, but there are a few breweries here.
Pie Hole has great pizza and $1 PBRs !!! yum. and it's open til 3.
Unfortunately (or not) Idaho has the highest mormon population per capita, but rest assured that doesn't really interfere with the nightlife. Good independent theater downtown. One of the best farmers markets I've ever been to, great co-op, huge Basque population. Boise's sister city is in the Basque region of Spain. There's a really high refugee population, I'm not quite sure of the reason. There are ski movies coming through town every year, banff film festival, basque festivals. Great concerts, Dave Matthews comes through, Michael Franti, the Rolling Stones came a while back. They have sports teams: Hockey, baseball, Boise State Football, basketball.
The North End was rated one of the best neighborhoods in the US by the American Planning Association. Right now, houses are dirt cheap here so buy something in a nice neighborhood (North End or East end).
You're also moving from Portland, probably the nicest city in the US. Boise is much smaller. Still has everything you need, just not as much.
Climate is really dry. It doesn't rain much, but when it does, it pours and is really beautiful. You get those rocky mountain thunderstorms to accompany it. If you like the ocean and can't bear to part with it, well, this place is pretty landlocked.
It snows about 20 inches cumulative each season.