While K100D is a natural upgrade from DL/DL2 it's a really hard case when you have DS... Joele summed up what you get and what you loose...
In your place I would wait (I also have DS and I wait). I would not be surprised at all if Pentax would introduce an upgrade for K100D quite soon (let's say end of 2007). Gap between K100D and K10D is very large it looks for me that Pentax took out pentaprism viewfinder and larger buffer out of K100D to make room for future upgrade, kind of crippled K10D version in a K100D sized body.
So, I still use my DS and waiting what will happen in 2007
Also I don't rule out scenario that after handling in shop K10D I would go for it...