I'm not surprised at all with the responses here - they've been nearly all DSLR owners and virtually nobody would change what they did. Like I always say, it's tough to find an unhappy DSLR owner!
The only camera I've regretted was my Minolta Z5 5mp 12x zoom PnS... it was very fast and good in many ways, but the noise levels were unacceptable and I was extremely happy to be able to get a DSLR with lens for only $367 after rebate less than a year later (and sell the Minolta for a decent amount, bringing the price down further.) In retrospect, I could have held on to my original Fuji 2800 6x zoom for a little longer before making the DSLR jump.
On my third DSLR, I wouldn't change a thing... I may actually send my K20D in for service in the next couple months; I recently noticed that the AF is slightly off, adjusting it in the custom menu suddenly made my Tamron 28-75mm a much more pleasing lens to use (it's fine with the tweak, but it might be nice to have it properly calibrated while it's under warranty), plus I may have the sensor checked, a few of my extreme-ISO shots with expanded DR from Disney showed odd noise in the bottom; of course, with the DR on, you're looking at something like 12,800 ISO in the shadows, but again, might be nice to have it 100% checked. But really these are minor issues, if all my equipment got destroyed somehow, I would definitely buy the same camera today, no question whatsoever. Heck, the weathersealing alone has come in amazingly handy, I've been surprised how many times I've found myself taking photos in the rain lately. (Some of that is upstate NY weather for you...)
The lens question is a good one. I have one or two used lenses that I regret, but nothing that I really detest. It's nearly confirmed that we'll see a FF Pentax next year but I really don't have FF lust at this point; I love the size and weight of the K20D, and the 50-135mm is a great lens, giving the equivalent of the usual larger and
much heavier 70-200mm lenses for FF bodies (and it's far cheaper, if you compare OEM lenses, and right now, I want the weathersealing enough to not seriously consider the Sigma/Tamron.)
I really don't use my Zenitar 16mm fisheye very much any more, but don't regret buying it. My Vivitar Series 1 70-210mm F2.8-F4 will probably be going on eBay soon, it's a very desirable heavy metal MF lens but the focus is just too sensitive for my tastes; fortunately I can probably sell it for more than I paid for it. I don't really use my older "basic" 18-55mm or 50-200mm lenses but they're nice to have around, my wife uses them on the K100D often. The Tamron 28-75mm F2.8 will be going up for sale as soon as I get around to buying the Pentax 16-50mm F2.8 - I wasn't really happy with the Tamron on the K20D but things are much better after adjusting the focus. Regardless, I still want to be able to go wider, and want the weathersealing, too.
Now, my best lens buy lately has to be the Lester A Dine 105mm F2.8 1:1 macro... since I bought it less than a year ago, it's become even more legendary and the costs have gone up about 2.5x what I paid for mine! It's really a stunner, and I couldn't justify paying what it goes for now so I'm glad I got in when I did! It will
not be going up for sale in the foreseeable future.
