"Directx10...Worth it?"
That would depend on your Hardware (and most importantly, video card), Game, Patches, Drivers
The answer is very subjective. Some people say they haven't noticed a difference between DX9 and DX10, but do notice a performance drop when running games under DX10.
Do note that only DX10 games can use DX10. However you can also run them under DX9 as well, in Vista.
My examples,
Crysis: It ran fairly well in DX10 on semi high settings till the last level, where I got massive stuttering and had to switch to DX9 mode to finish the game. Did I notice a difference in visuals? Not enough to make me wish I could finish the game in DX10.
On the other hand,
Lost Planet: Colonies Edition, yeah, I did notice a difference in visuals between DX9 and 10. DX10 seemed to be more vibrant and details like the character’s fur stuck out. I was able to play that game without any problems all the way through.
Crysis Warhead, I played it all the way through the end under DX10 with little problems under "Gamer" settings. Nice visuals
Bioshock - didn't notice a difference either way, and I played that game all the way through twice. In fact the first time I played the game I played it with a DX9 only card (Radeon x1650Pro). So when I got my Radeon HD 3870 DX10 card, the first game I wanted to play was Bioshock as I was looking forward to the "added DX10 visuals" ....well, I didn't see them, especially in the water and oil spills, to me they looked the same. So...
So...If you have Vista and a DX10 card with a DX10 game, play in DX10, but if you have frame rate or stuttering problems, switch to DX9 mode. You may or may not notice a visual difference, but you'll probably notice a frame rate increase.
So...the question now becomes... frame rates or visuals?
Just my opinion,
…and by the way, I am a visuals type of guy
