Originally posted by Nicolas06 I also think you'd want the 2 wheels for your camera this really is invaluable in term of efficancy, control and ergonomics. More buttons is also better overall, you might never need them all or don't care but if we speak of "grow", then having more buttons and more modes is something that help make your camera practical and a good tool.
So I'd say like stavri a K5/K5-II/K5-IIs (pro line with more buttons) or a K50/K30 (entry level line but with 2 wheels well made still and lighter).
Totally agree for stills.
The cameras mentioned above are also weather resistant. They all also have a larger grip then the K-S1 and, in the opinion of many coming from older PENTAX DSLR's, a more ergonomic one. This coupled with their extra weight makes them better I think for use with 450gm plus lenses. If however you think you will be doing a lot of video then the K-S1 has its merits.
A lot however depends on your budget and how soon you need your DSLR. If you need it now then, from your selection, I would probably choose the K50. If you could wait a bit longer for the K-S2 price to reduce (it's bit expensive at the moment being a new model) this may be a better choice for you. It has everthing and more than the K-S1 It is weather resistant, has two wheels and has a large and more contoured grip.
Incidentally, where are you coming from: smart phone, family compact, enthusiasts compact, bridge camera, film camera,etc.? Your answer may allow others who have made such a decision in the past to give you the benefit of there experiences.