I mainly use zooms because I shoot a very wide range of subjects (many of them moving) and at a wide range of distances. For closeup work I have an EF-S 60mm f/2.8 macro and for portraiture I have an EF 85mm f/1.8. For most other shooting I don't need the wide aperture that primes can offer.
If you're okay with the 7D's noise profile at high ISOs then you won't go wrong with any of the Canon f/4 zooms. I've owned a few of the 70-200s (both f/4s and the 2.8 IS) and the 24-105 and always got a much higher percentage of keepers with the 2.8. At the time I was shooting a 40D, which has a high-precision cross-type sensor for f/2.8 and larger aperture lenses (the center point). Maybe that's why I did better with the 2.8. I was shooting a lot of tennis, daytime but also under stadium lights, which can be pretty demanding even for fast glass on 1-series bodies.
But that's the only reason I'd think about the 2.8, to have that high-precision sensor available. The 7D's AF is quite a bit better than the earlier Canon crop bodies though; it has the same high-precision center point but also all 19 points are 5.6 cross-type sensitive, which is pretty cool. On the 40D there are only 9 such points. The arrays on the 2 bodies are the same size but the 7D's is twice as dense. If you're happy with your keeper rate now
then you won't miss the 2.8 sensor. If that's the case I'd grab the f/4 IS. It's a nice lens for everything but action or low-light candids. Of course 2.8 gathers twice as much light as f/4 ... and IS doesn't do a thing for subject motion... They say the best camera/lens is the one you have with you
so consider the weight of the 2.8 before you buy it. If that stops you from grabbing it on the way out the door... Me I accepted it right away, the first day once I saw the bokeh and the action-stopping shots I got with it, shots the f/4 could never give me. But carrying it around all day is def a commitment. A monopod can help (though I rarely used it with the 70-200) but of course a monopod is another thing you'll have to carry.
You sound like you know your shooting style and preferences pretty well. I'd only suggest thinking a bit about whether you'll ever want to expand into low-light or action photography (sports, kids running around, etc) where fast glass really earns its keep.