If you buy a wal-mart bike and find out it isn't for you, you won't be able to sell it for much. On the other hand, if you invest in a nicer bike and want to sale, you will recoup more of your money. Also, something to think about it...cheaper bikes from wal-mart tend to be heavier and more difficult to ride. So if you get one of these and decide biking isn't for you, it could be that you aren't using good equipment. So, I say invest if you can afford it. In the end, the most important thing is conquering that last frontier :-)

*This is from my experience...I have a Schwinn Cruiser Hybrid ($200 from Target) collecting dust in my apt because I don't enjoy riding it.