Yeah, I've just checked the prices. 70-300 non-L at B+H is $650, 70-200 f/4L non-IS is $630 including instant rebate.

When I bought miine, however, the 70-300 non-L was closer to €400 and the 70-200 f/4L was at €550 or so. With that kind of deal I opted for the IS over the constant f/4 and L-quality.
But if you're looking at practically the same prices like you are today, then yeah, i'd get the 70-200 f/4 L as well (or save for the 70-300L, which i did)