I'm not sure I would consider myself an expert on Vientiane--I lived there for a month and just moved back to stay for a while. Other than a few places in Thailand, I haven't traveled extensively throughout SE Asia, so I can't compare it to other places in the region. I haven't been anywhere else in Laos, but hopefully that will change soon. To start off the discussion, here's a brief list of the pros and cons of Vientiane:

Pros
Hot falang-loving women
Cheap booze
Safe if you aren't a [censored]
Wide variety of cheap and tasty food
Friendly people
No "damn falang" attitude like Thailand
English is widely spoken

Cons
Limited freedoms and rights
90% of the city is shut down by 9:00
Except for 2 or 3 places, bars close at 11:30
Poor medical care
[censored] tuk-tuks
Sexing Laotians is illegal (though rarely enforced)
Internet is expensive and/or unreliable and/or slow

To give you an idea of the cost of living, here's what random things cost in US dollars:

Small bottle of water--$.20
Large beer in a bar or restaurant--$1
Fifth of Jameson in a store--$16
Meal in a local place--$1
Meal in a western-oriented place--$3-4
Meal at nicest place in town--$10 an entre
Personal Trainer--$5/hr

So ask away and I'll answer as best I can or talk to someone who knows what's up. I don't have internet at the place I'm staying at right now, so it may take a little while to respond to questions.

Why did you go? I'll keep my assumptions to myself for now.

I came for a brief holiday/Thai visa run, ended up loving it, and stayed for a month. I then spent a month in Bangkok, didn't care for it, and came back.

Thanks for doing this
My questions:
how is the climate and how bad is pollution?
what do you pay for rent?
what kind of activities are available (like golf, tennis ...)?
what are the visa regulations?

The climate is tropical, very similar to Thailand. Right now it is HOT. The heat in Thailand never really bothered me, but here it seems like I'm drenched in sweat after walking a couple blocks. Maybe I should start wearing shorts. It should cool off soon, though. Supposedly this is the rainy season, but it's been dry for few days I've been here.

There's not much air pollution because there isn't much traffic here. Vientiane is a very open city and there are plenty of trees.
When I stayed here last time I worked out a long-term deal at a decent hotel (air conditioning, fridge, double bed) for $55/week and I'm doing a similar deal right now. I want to find a house or apartment in the near future. I should be able to find something nice in a central location for $200-300. I could pay more but I don't need 3 bedrooms or anything.
There are a couple golf courses in the area. I'm not really a golfer so I can't comment on how they are. I hear there's a bowling alley in town. I've seen badminton, squash, and volley ball. I'm pretty sure you would die if you tried to play tennis in this heat. I've played a couple times when it was over 90 degrees and it wasn't a pleasant experience.

There's an expat rugby team called the Vientiane Buffaloes. I'm a little undersized to play rugby plus I don't know many of the rules, so I don't think I'll be joining the team.
30-day visa on arrival for about $35. This can be extended for (I think) 15 days in Laos. If you want to stay longer you need to leave the country and reenter.

When I was typing the above, two ladyboys approached me and asked if I were interested in doing commercials for Lao TV. They gave me a card and took my email so there's a pretty good chance they're legit.

For some reason "legit" and "ladyboy" in the same sentence give me headaches

Pics of
plzktx

"No "damn falang" attitude like Thailand"

I've never heard this before...could you elaborate?

Predominate mainly in Bankok. The last few years have seen a small but noticable angry nature for some lower class Thais resulting in some outward hostility towards farangs. Of course for Thais, any outward hostility is V bad/major loss of face, so the expression of the hostility is more like an angry look or word rather than violence one might find in other countries. But, from most reports of said instances, it's mainly restricted to BKK and lower class Thais. In 4mos, I haven't seen even one instance of it on Phuket Island.

SE Asian women don't photograph well (i.e. they're much hotter in person) but I'll try and track some down. I've seen a number of formal portraits where the girls are wearing a silk skirt and silk top that leaves their shoulders and stomach exposed. I think this is the hottest thing ever. I tried doing a google image search but I'm not sure what it's called or what to search for.

Random Lao hotties:

Can you expand on this plz?

There's no freedom of speech, a one-party system, corruption, etc. They're very laid-back about it, though, and you can generally do what you want other than demand your right to do what you want. If they wanted to, the cops could arrest you for some BS reason to extort money from you and it's not like there's an ACLU you can call. The only English-language newspaper is owned by the government and is frequently hilarious. Rice farming looks awesome! The Bangkok Post is available so it's not like North Korea or anything. Web censorship is about the same as Thailand. I tried to find some quotes from organizations like Freedom House, but the sites were all blocked. I don't know what it's like outside of Vientiane other than Luang Prabang has a midnight curfew.

This alone sways me to thailand haha.

seriously though, has it ever been a problem? kind of negates the whole "falang loving women" thing.