Size: Vancouver is a "big" city (or at least tries to be), but it's still pretty small. Small in a good way though, the population is ~2m in the metro area but the city itself is ~600k. The downtown core is completely walkable. It's always more of a hassle to hop on the train for 2 stops than to just walk. Clean, can't recall ever seeing poop (human or animal) on the sidewalk.
Rent: for downtown living in the more expensive parts, you're probably looking at $1600-2500 cdn for a 2bdrm. Don't mind commuting 10-15 minutes on the train/by bus: $1000-1600 for a decent place. You can get a studio or 1 bdrm in the west end (downtown) for $800-1200, add a few hundred more if you're looking at coal harbour/yaletown.
Outdoors: Parks, everywhere - a couple large ones and tons of small ones (a couple soccer fields, running track, etc). You've got more ocean than you could ever ask for and a couple local mountains (~20-25 mins from downtown by driving, or take transit + gondola up grouse which will probably be an hour or so). And you're 1 hour from Whistler. Lakes and camping within an hour of the city. There's also Stanley Park right downtown. One of the biggest advantages seems to be that you can get outdoors and feel 'out of the city' within the city limits.
Entertainment: Hockey (NHL/WHL) and Canadian football. Same amount of large bands coming through here as any major US city, good small venues as well for some local bands and smaller acts.
Transit: The city has pretty decent transit and it's cheap. $2.50 for a transfer (last 1.5hrs) or ~$80 for a 1 month, unlimited 1 zone pass. There are 3 SkyTrain lines which will get you downtown pretty quickly from anywhere within Vancouver (15-18 mins max). Transit is pretty bus-oriented, but it's never really been a problem for me. Getting out of downtown might be a problem if you like to hang out past 2am and/or live in the sticks. Not much open 24 hours or really late other than a couple coffee shops and a handful of restaurants.
Biking: I don't bike but the city seems fairly bike friendly (and getting better), I believe we have 3 routes now with separated bike lanes downtown. You can bike safely from anywhere within Vancouver. My neighbour bikes to work every day from East Van which probably takes him 25-30 mins each way.
Tech Scene: It's alright, but we're working on it. I put together a startup hackathon last month and met a bunch of fellow Vancouver HN users. There are a couple startup incubators here and more coming (I believe), Bootup Labs seems to be the most well known. There are angels, VCs and the like here - but nowhere near the level of SF, NYC, Seattle.
Talent: 2 main schools with CS programs nearby (SFU and UBC), but talent seems hard to find - it's here, you just need to look. If you do find it, it can be fairly cheap though. Much much lower than the valley (from what friends have told me), there are no Facebook-like companies driving up salaries here. I'm probably going to get shanked at the next hacker meet up, but you can probably get decent people for $35k/yr (junior) to $70k/yr (senior/leads).
A big problem seems to be that you can count 'notable' startups on one hand. There are gaming companies here, both mobile/console and gambling. It's much more relaxed here and people just want to live life well. There are hardcore entrepreneurs and hackers here, but also a lot of wantrepreneurs and people who want to come in at 10, take an hour lunch and leave by 5. Very little of that 'startup culture' you hear so much about in San Francisco.
My opinion, but other Vancouverites feel free to criticize or add to this.