Sigma 24mm f1.8 on FX

Re-posting this here as everyone's abandoned the lens forum for now!

I'm about to upgrade from DX to FX (looking for a used D700). I'm a big fan of wide-angle shots with shallow DOF. Naturally my ideal lens is the 24/1.4G, but that's way out of my budget for now.

What about the Sigma 24mm f1.8? It's a lens you rarely hear about, but the snippets I have heard suggest it will suit me well - and it's a fraction of the price of the 24G. I don't need corner-to-corner sharpness, as generally my backgrounds will be out of focus anyway. Good central performance wide-open (or close to wide-open) and good bokeh (for a wide-angle at least) are more important to me.

Given my usage, is this a recommended lens? How does it compare at 24mm f2.8 to the 24-85 f2.8-4, which is another lens I am considering?
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Pete
http://peterbrockwell.zenfolio.com
http://www.flickr.com/photos/pete_mb/