OK, now I've switched to dx9 the performance is
much better. I'm getting mostly smooth framerates at 1440x900 on Gamer with 8800GTS overclocked. I'm maybe a bit dissappointed as ppl with lesser machines running same res at Enthusiast but I like silky frame rates. I can't see the point in eye candy at 15fps plus it makes the game a lot less fun.
Those having problems with distorted sound should look here:
http://www.crymod.com/thread.php?threadid=21588
On the whole I'm really enjoying this game especially now I'm running DX9. I've been trying to not rush through it. Making the most of it as it where. and some of the levels are just amazing. You have to punch the graphics upto enthusiast when the train goes through the swamp

It looks absolutely amazing. I've probably played it on normal difficulty for 4-5 hours so far but it looks like I'm getting near the end as the cut scenes are getting longer and thats a sure sign.
Load times.... Oh come on, their just not fair. Those load times aren't really acceptable. We mostly have fast HD's and 4GB's of ram. Why are we waiting 1.5 mins to load a level or change graphic settings and the game takes just as long to start!
In short this is a good game but it is just an expansion pack for Crysis. A Crysis Ep1 if you will. It is not an evolution and certainly not an improvement techically but it is good fun.
My main comment is that although DX9 runs better and DX10 looks
slightly better is that I thought when DX10 came out that the focus with the new API was to increase efficiency and therefore performance? I understood that the focus was particularly on repetitive tasks like grass/trees/fences or anything like that needing only the be rendered once and then "stamped" if you like all over the game scene. Most of the previous API's introduced features to improve quality and use new features (HW T&L, Shaders etc) but DX10 was supposed to be different.
Microsoft: You fail
Seriously though, I'm not going to jump on the Anti-MS bandwagon as it's far too easy to do and they have no control of what ppl do with their API.
I would though, be very interested if anyone has any thoughts on why DX10 is soooo much slower than 9 when it really shouldn't be?