Has no negative affect at all - the search engines treat hyphens as a space.
Using hyphens can help legibility for humans though, so its worth considering that factor, particularly if you are going to end up running lots of the same letter together - eg wellliving v well-living - but as has already been pointed out make sure you can use both hyphenated and unhyphenated versions to make sure you don't lose visitors not using the hyphenated version.
www.dvisions.co.uk - lose the camouflage and stand out...
From an SEO perspective hypenated domains generally make no difference. In fact, it makes the keywords in the domain even easier for the engines to distinquish. It eliminates any ambiguity... For example expertsexchange.com could be considered an exact match for "experts exchange" or "expert sex change". With experts-exchange.com, there is no ambiguity.
However, from a user perspective I think domains with hyphens are seen by many users as less legitimate. Many searches associate those domains with spammers, affiliate marketers, and the like. They know that they were take as a last resort because the non-hyphenated domain was no longer available. It's similar to the way that users perceive .com domains as more legitimate than .info, .net, .biz, etc.
I agree with Stevecane. I have 1 in my domain and I leave my competitors for dead! It has had no negative effects what so ever.
Peter Watson is the founder and CEO of Business Trader - Buying and Selling Businesses in Australia.
Do the best you can - as fast as you can - then fix it later.