Yes, getting a 3G right now would be a bad choice.
With the new iphone releasing in 2-3 months I wouldnt purchase a 2 year old iphone that wont be able to run most 4.0 iphone OS features that are to be released.
Right now the 3G is $99, 16GB 3GS is $199 and 32GB 3GS is $299 if you're eligable for an upgrade or open up a new line.