There is a way to look up your flash online somewhere to see if it'll work with your DSLR. My old full-manual flash from my K1000 works fine on my Pentax DSLRs, but you have to shoot in manual mode, since you set the flash to a specific aperture and ISO. (Actually, shutter priority may work, too.) I did find that going to a modern flash was much nicer to use, but if you're willing to take the extra few minutes to set the old-fashioned one, you can still get the big advantages of an external flash - more power and the ability to bounce it.
The K10D is an
astonishing bargain at the moment, it's really built to compare with the Nikon D200 (though I think the D200 has a faster burst rate) and has the same sensor as the D200 - only the Pentax's has image stabilization so every lens will be stabilized, whereas the D200 requires you to buy stabilization on a lens-by-lens basis, which means more money and most lenses just plain don't have it available. It's also weathersealed, which the Nikon isn't. (And sensor-shake dust reduction, the ability to do full P-TTL wireless flash via the onboard flash, etc.) Since the K20D is out now, the K10D can be had for incredibly cheap, and it's still a terrific camera with very few drawbacks.
The K200D will probably cost about the same money and is a similar camera in many technical ways, but is more entry-level, with only one control wheel, a smaller viewfinder, AA batteries instead of lith-ion, scene modes (like on a PnS), etc.
For buying, you may want to check
Amazon, too - I think they have some of the cheapest prices on the K20D and may be similar on the K200D, too. Their 30-day price adjust policy can help you - I got back over $150 after they dropped the price of the K20D after I bought mine. If you end up with a K10D, I'd recommend buying soon - they will probably all disappear soon. If you decide on a K200D, you may want to wait a little while as it's brand new and the price will surely drop over the next few months. And in fact, rumors are that we'll see a cheaper K2000D introduced later this year, but details are mostly speculation at this point. The K200D is a little higher-line than most other entry-level DSLRs and is not priced cheaper, as opposed to previous Pentax entry-levels, which were usually cheaper than competing DSLRs.
Oh yeah, in case you hadn't guessed, I think everyone will recommend a DSLR over the other cameras you mentioned, especially if you're already used to a film SLR. The digital point-n-shoots will not give you the image quality (especially in low light) of a DSLR, but they can take movies and are smaller and often have huge zoom ranges which'd cost a bit of monet to replicate on a DSLR.
Kevin, the Canon 50mm F1.4 isn't quite twice as much, but close. (I think it's $300, the Nikon is slightly cheaper, the Sony is slightly more.) But everything I'd read does say that the Pentax still has the edge, even being cheaper.
I'm going to guess that WVDisGeek has a manual-focus 50mm F1.7 or maybe even F1.4 - both top-notch lenses. (Some even argue that they're even better than the current lens, but I think the differences are so slight that there's no clear winner - though the old all-metal lens certainly has a build-quality advantage over the plastic-body current lens, although the current one still does feel quite nice.)
Mark, supposedly "bulb" modes comes from the early days of flashbulbs - the photographer would open the shutter, manually fire off the flashbulb, then close the shutter. Who knew?
Anyway, I think bulb mode is extremely rare in a PnS and remote shutter releases are similarly rare.
