Have you used a Sony? I haven't, but I can't imagine it being any worse than holding an Olympus or Canon. It's supposed to be quite good ergonomically, although I don't know what to think about that top left dial (when looking at the A100 from the back). Again, I hear it's good.
And while everyone who says Sony's camera doesn't have as many lens options, I'd guess that in the next 1-2 years, you're going to have all the lenses that you want. I mean, if Sigma, Tamron, and Tokina start making lenses for the alpha mount or whatever it's called, and Sony/Zeiss/Minolta continue making lenses for Sony, then they really are covered.
I really don't think Sony is going to be out of the DSLR game any time soon, and I'd even guess that their lens lineup will be good enough for you to get the lenses you want, along with accessories in about 2 years.
However, there currently isn't a lot out there for Sony, but I think by Christmas time, we'll see lots of accessories and maybe a few more lenses.
And if their camera is competitive with Canon or Nikon, I'd say they have a good chance of being bigger than Pentax and Olympus faster than you'd think. The only thing that'll keep Pentax alive in 10 years is their deal with Samsung.