I have a special place in my heart for those "sidewinder" Genesis 300 grills. I agree with Larry that they were, in some ways, the very last gasp of the classic Weber design. (You could, at that time, also buy Chinese manufactured Weber Spirit grills that still had the original Weber design underneath.)
Anyway, I appreciate Bruce's sharp eye, so for sure look it over well. I wouldn't pass on this overall rather pristine example if there is just a little surface rust on that leg. If it looks like it is ready to rust off, that's another matter. Rusty floors, rust on the cabinet walls, and especially failed frame legs are what do in most of these. Still a REALLY nice grill if you are diligent to care for it and preferably store it out of the elements.
I had the next model front control Genesis 330 with the sear burner. I have to admit that I personally did like that feature. That's why I always hope to have more than one grill on hand! I think each design has its merits. I suppose if I could only own one of these, I would choose the one posted here.
The sear burner proved to be a popular addition, and after a short drop when the Genesis II came out, it has been a staple ever since. They really highlight it now with a red control knob on the newest Genesis model. We can argue about thin fireboxes and rust-prone wrapped steel in place of true frames. Those are valid observations. I guess Weber has concluded that most people figure a grill is at best a 5-to-7-year proposition, and accordingly they don't see the point in building a grill that can last 20.