Windows 7 is definitely the way to go if you're thinking about buying a new machine.
In terms of it's usability it is not harder to get to grips with at first than Vista is, and whilst it is similar to Vista in many ways, it also does away with many of the complaints people had of Vista, namely it's penchant for hogging all your computer's memory even when you weren't doing anything with it. As a result, Windows 7 will run smoother and more responsively on the same hardware when compared with Vista.
If you shop around, the price difference isn't all the much in many cases. Toys 'R' Us isn't somewhere I'd ever buy a PC from, but as an example, they are selling a Toshiba laptop with Windows 7 on it that has better spec than their Vista equivalent, and it actually costs less to buy. I have seen similar deals though. Either, having purchased Windows 7 myself (am using it now) after testing it for a lengthy period, I would wholeheartedly recommend it over Vista if you have the choice.