Originally posted by Edward B. I have to agree a little bit.
I can't read the OP's mind, but it looks like he's in a similar boat that I am/was.
Really likes the feel of the Pentax, but is worried about some things he's read, specifically the poor autofocus of the Pentax.
I think what he's asking for is if the AF is acceptable or if he should go with the XSi, which has a leg up on that issue.
I don't think he's posting to rub in the fact that he's considering buying a different brand.
Just my take on it. I also have to add that overall I've found this to be a very helpful place and a lot more useful than other camera forums out there as people seem to be more interested in providing genuine thoughts instead of launching into attacks.
Edward, the OP's post contains valid questions and seeking for advice. I think, that has been addressed in the following posts to any sensible extend. But for another poster declaring, that old and outdated cameras like the 30D or D200 provide better IQ than a K20 and would be superior choices is simply nonsensical. Apart from that, most of the problems the OP addressed stem from using a lens, which is not up to the job and will never provide the performance he expects.
So, it does not matter, whether he goes with a D90 or K20, unless he also invests considerably more money, than the camera body will cost, into lenses, which are up to the task. I think, this is a sensible message.
Ben
P.S.: Nevertheless, I in general think, that some recent threads have been too heated and I don't no why. Perhaps it would be better to deal with uniformed provocation (and that is not aimed at the OP!) by simply ignoring it.