Okay you don't need "insanely fast shutter speed" just for bright conditions. You can use a lower ISO setting or stop down the lens. That said, "insanely fast shutter speed" is really not that big of a camera feature anymore. 1/1000 is about as fast as you need and it's available in every point n shoot there is.

For what you've said I don't see what you need an SLR for. Nature shots aren't particularly tough and you don't need a really fast shutter speed. Usually you're going for lots of depth of field and that means stopping down the aperture which cuts the amount of light just fine. Plus you're going for the most detail so you use the lowest ISO setting which means less sensitivity to light as well. You don't need a quick shot-to-shot time because you're not taking action shots, and this bullet picture you're talking about requires tricky stroboscopic lighting and a studio.

For landscapes and whatnot you're generally using wide angle or standard lenses which for dSLRs with crop factors get rather pricey rather quickly if you're looking for something quality. The other weapon of choice for a nature photographer is a good macro lens for focusing up close on flowers, bugs, whatever. Again, not exactly cheap for a dSLR.

A whiz-bang camera body with only one so-so lenses is not going to do you much good. If you're gonna step up to the plate and go for a proper set of lenses then fine. But if not then you'd be better served by a compact camera with a good sensor, nice lens and macro capability. Say, the Olympus C-8080. Its overall image quality is very good, its lens gives you an angle of view at the wide end equivalent to a 28mm lens on a 35mm film SLR, its ISO settings go all the way down to 50 for when you're in bright light, and it has a macro setting for its lens that allows you to get nice and close in on small stuff, it's made mostly of metal, and it costs the same as one quality "standard" zoom lens for a dSLR. No, it won't take silky-smooth images at high ISO settings, but it doesn't sound like you're going to do that. And it won't let you take 5 pics in one second, but it doesn't sound like you're going to do that either.

Let's look at lenses for a moment. The cheapest good macro lens for a dSLR is a Sigma 50mm f/2.8 EX macro. $269. Next priciest would be a Sigma 105/2.8 or Canon 60/2.8 EF-S each at $399. Now, all these choices would probably be better than a macro mode built into the Olympus C-8080 so just for kicks a cheapie Vivitar 100/3.5 macro is $149.

Wide angle? 28mm on a full-frame camera is 17mm for a Canon dSLR with a 1.6x crop factor. The cheapest zoom of any decent quality level that goes out that wide is the Sigma 17-35/2.8-4 which is $399. There are some assorted rather crappy lenses that go this wide, but well, they're rather crappy. There's also the Sigma 18-50/2.8 at $499.

So let's say you go for the Sigma 17-35/2.8-4 and the Vivitar macro, you're out $550 just on lenses and you don't have the same range of coverage as the Olympus C-8080 on the wide end, plus you have a gap from 35mm all the way to 100mm. Spring the extra hundred bucks for the Sigma 18-50/2.8 and you've narrowed the gap a bit.

If you wanna spend the cash then fine. But for the pics you've talked about that are readily achievable with any camera, you're not gonna really see any difference.