Secondly, I think they're good to have because they're a 24/7 advertisement and source of information about your company. You can put your web address on all your marketing and invoicing materials... business cards, flyers, door hangers, estimate forms... everything... then, you put all the information on your site; list of services, pricing information (if you really want to), your service area, etc... people have access to your info any time they want it. You could even put discount flyers online for your potential customers to download and print themselves to redeem when they call on you for services. That way, you save ink! =)
On the other side of the coin, you can't control EVERY aspect of the design on MySpace... there are certain things that will come up whether you want them to or not... and your older customers will not know anything about MySpace...
Use MySpace, but don't rely on it as your only source of online presence.
The YellowPages are good, too, if you want to pay that much. I think the YellowPages are probably the MOST expensive "basic" advertising you can do (unless you consider TV and Radio commercials "basic" advertising)... my company is not in the yellow pages... it's just too expensive for me right now... maybe in a few years... but not any time soon.
I hope this has helped you... sorry if I was a little too wordy and long winded... lol
Feel free to ask ANY and ALL questions you may have... we're all here to help you along the way... we all help each other. = ) We may even learn something or get ideas and inspirations from you as well!