Rebecca's absolutely right. The sky is the prime subject, and the placing of the horizon line exemplifies that.
The upper right cloud's exposure is blown, but you can rectify that by cloning some of the lower light gray clouds to better balance that area. Then your eyes aren't constantly being pulled there by the overexposed portion. Very dramatic sky, and well composed.
Thanks everybody for the kind comments....the funny thing is I did not realize how cool the sky looked at the time. Only after seeing them on the PC and doing a bit of tweaking (using Picasa) did I say "yessss". The only thing I did was drop the shadow density and do some cropping. Down the road I plan to spend a little more $$ on a higher-end Canon..I assume that better sensors mean fewer blown-out highlights? Mine is a SX10IS, which is considered to be consumer grade stuff...it's no rebel. The other limitation of the SX-10 is it has no filter ring, as a polarizing filter can really make sky colors 'pop', while limiting glare.