it certainly seems to, from looking at SERPs. I have seen realy positive effects from renaming pages to keyword.html or keyword1/keyword2.html but you can't run that kind of test on a domain name.
I cant verify this but from my experience Google doesnt really give any weight to keywords in the domain name but Yahoo seems to.
KW in the domain does aid SEO, but I don't think it carriies as much weight as it used to. It's best to go with a kw1-kw2.com (co.uk etc) don't do what some people are doing and going for kw1-kw2-kw3.com because it just stands out as being spammy IMO.
Yes, it does indeed, although not as much as other places such as title but more than meta keywords and description (at least for Google and others).
IMO, it helps quite a bit. Although there's not much you can do about it if you already have a website. But, it is a good idea to register a domain that contains keywords that you are looking at targetting. Relevant file names also help, but try not to overdo it. Ex: www.kw1.co.uk/kw2.htm is fine but www.kw1-kw2-kw3.co.uk/kw1-kw2/kw3-kw2.htm is overkill Having said that, if you get a high enough PR, you can rank well for just about anything. I have exchange links with websites (for my company sites) that have got nothing to do with our "theme" or our "keywords", but they appeared in the top 10 results within 48 hours of our getting those links. So, all this talk about relevant links and importance of keywords in the URL etc is relevant and important only if you have a low PR. But, as soon as you get a high PR (high depending upon your industry, even a PR5 could be good enough for certain industries) you can stop worrying about all this and watch the traffic come in!
I've seen the same as you -- one of my website's domain names is totally unrelated to the keywords, yet each of my optimized pages ranks in the top 10 on G. In my case, it was all about on-page keyword density and PR, not the domain name. That said, I would pick something that will be easy for your clients or visitors to remember. Once you get a bunch of hyphens, etc., it gets confusing ('Do they have hyphens or not?' 'Was it plural or singular?'). Another website of mine has the keywords in the domain, and it ended up being so long that I wish I had done it differently. And it didn't seem to help in the SERPs. Best of luck, StacyO