Let's see... where to begin. Obviously, IS is hardly a magic bullet that will cure all blurs - you'll generally pick up 2-4 stops. Try shooting with a non-IS lens at twice or four times the normal shutter speed (ie, 1/100th and 1/200th instead of 1/50th) and see if it's enough to stop the shakes. Regardless, there will probably still be situations where IS won't cut it. This especially includes any photos of moving subjects - IS might sharpen up the static objects but you'll get more blur on moving things thanks to the slower shutter speed.
For IS in the body, you can choose anyone other than Canon and Nikon, who both still refuse to put IS in the body (though I'm sure they'll come around one of these years!) All current Pentax and Sony DSLRs have it and the Olympus E510 does as well. Olympus has some of the more interesting lens options (faster zoom lenses than anyone else) but they are very pricey.
In the Pentax line, there is not currently a 70-200mm F2.8 widely available. Pentax had their own
very nice 80-200mm F2.8 until 2004, and currently has a 50-135mm (roughly same coverage on a DSLR as the 80-200mm on a 35mm) F2.8, which has ultrasonic focusing and weathersealing. It's $750 at Beach. As was mentioned, they have a 60-250mm F4.0 in their lens roadmap, it'll probably be announced on Jan 24th along with their new DSLRs and other lenses. Sigma did make their current 70-200mm F2.8 in Pentax mount but availability is scarce, but they come up for sale fairly regularly, often around $800-1,000. (The "marketplace" at Pentaxforums is a good place to check, I've bought a few lenses from there.) They have announced an updated version of the lens so hopefully that will have wider availability (and lower price!) Tamron has been promising their own 70-200mm for at least a couple years with no release yet, but based on how good their 28-75mm F2.8 is, I'm anxious to see it available.
My solution was that I just recently bought a used Vivitar Series One (their pro line, very expensive when new) 70-210mm F2.8-4.0 lens in Pentax mount. It's manual focus but otherwise can stand up well against the others, with really nice image quality and a terrific build. And my K100D treats it as a F2.8 through the range, I was taking some 210mm F2.8 photos just the other day with it. The downside is that it's new enough to have an "A" aperture setting (so no need to manually set aperture) but it's not new enough to transmit focal length to the camera, so IS doesn't work so well. Any time you attach a lens that doesn't transmit focal length, the camera lets you choose what focal length it is - but that isn't so helpful when using a zoom! It does work terrifically for prime lenses (and even adds the focal length to the exif data.) Still, I got it for around $150 and I can put up with those quirks for the image quality, solid feel, and fast aperture. Oh, one more negative - the front rotates when focusing, which is a big negative to me - it makes using a polarizer much more difficult. I figure it'll eventually be replaced with a modern 70-200mm F2.8 and I'll be able to resell it for at least what I paid for it, so no harm!
As for in-body vs in-lens... well, like I said above, I think it's only a matter of time until in-body IS is ubiquitous. There are virtually zero negatives, and if C/N want to offer in-lens IS in high-end lenses, it would be trivial to have the camera start enough to disable the in-body IS when using a lens with IS. Having the ability to have IS with
every lens is really great. (Especially with a camera as legacy-friendly as the Pentax... I can mount a top-quality 30-year-old Zeiss 180mm F2.8 screw-mount lens on my camera and it'll have IS, just like the 18-55mm kit lens, and the 50mm F1.4, and the Sigma 30mm F1.4, and so on and so forth.) There are also negatives to IS in the body, which are so rarely acknowledged... besides the obvious one (cost for every lens), Photozone.de has found problems with in-lens IS. "During the local lens testing it became obvious that IS/VR lenses tend to suffer from centering defects to a much higher degree than their conventional cousins." There's also an extra piece of glass that the light passes through, which is a negative optically (though most IS lenses are pretty high-end so that's not that big of a deal), whereas nothing is needed for the IS in-body. The big concern for me is reliability... anecdotally, I've heard of more problems with IS systems in lenses than in bodies. (Actually, I've never read of any in-body IS mechanical problems, though I'm sure they have happened.) There's some interesting discussion
here (check the comments too) and a zillion other places on the internet too. It's a debate that will rage for a long time to come (probably even after C/N start putting IS in-body!) Ultimately, I think it's mostly picking nits, any IS is better than none at all!
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, asked an interesting question this weekend. So I am coming to the boards to see what your opinions would be...
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