could you please elaborate on this..??
Assuming you can see past my "flawed logic" (as you wrote in your original, before-editing reply in another thread), I would assume that what Kevin means is that the Live View on DSLRs is never without compromises.
On basic systems, the mirror needs to flip up to view it, then flip down to autofocus, take the photo, flip back up, etc... noisy and mostly good for tripod or situations where it's difficult to see through the viewfinder.
Some, like the XSi, do contrast-detect AF so the mirror doesn't need to flip down to AF, but it's much slower than normal focusing and slower than PnS focusing.
Others, like the Olympus E330 and Sony A300/A350, use a second dedicated sensor in the viewfinder. That means AF in Live View is just as fast as normal focusing, but Live View no longer has 100% coverage, there's no image stabilization, there's no alignment overlays, no true magnification to help when manually focusing, and most painfully, the design means a much smaller tunnel-like viewfinder and on the Sony's, a smaller onboard flash which doesn't pop up as far, increasing the chance of redeye and the other unflattering things that go along with a flash near the lens and is more likely to be blocked up a lens. On the Olympus E330, the viewfinder is not only smaller but dimmer, as light is sent to both sensors at any given time, where the Sony has a mechanical switch to choose the sensor.
Point being, they all have drawbacks and none are going to be behave just like the LCD in a PnS.
Back to Kevin's message - as for ISO 1600, most are very good, though the Sony A350 is not all that good, worse than the 4/3rds sensors in the current Olympus models offers. See the reviews at Camera Labs for some examples. And I think the Nikon D60 is the only current entry-level DSLR to offer ISO 3200. (The Pentax K100D did, but the K200D doesn't, though the D60 and K200D use the same sensor.)
The XSi can't do ISO 3200 but I suspect you could get somewhat usable results by shooting at -1.0 exposure compensation and pushing it in post-processing. You can also do the same any DSLR with good ISO 1600 performance. I'm no Canon fan by any means, but the XSi is a very strong entry in the under-$1k DSLR field. Too bad it still has the usual Rebel "ergonomics".
