I have been very tempted by C1 since Kevin demonstrated it to me, and I played with it quite a bit, in Antarctica. It's fast, which is nice, its conversions appeared excellent and its use of layers is an interesting concept. The single thing which prevented me from changing to it from LR is that it lacks a history palette. I don't know why, and I gather it's not impossible that it will in due course acquire one, but for me at least that's a killer.
Jeremy
I used LR since V1 but never found the history function of any interest for three reasons:
1) LR's history recorded every tiny irrelevant detail. Increased brush size, decreased brush size, increased feather etc, etc.
2) In a pixel editor (PS) history makes sense. With a parametric editor, for me, it does not. If you decide an area is too bright you can step back in history until you find the brightening step but then you lose all other edits. With a parametric editor you simply darken the bright area, no need for history.
3) Layers allow you to organise your workflow into discreet steps which "contain" your edits for that area / type of edit, which combined with 2, further limits the usefulness of a history function.
Ian