In the case of the use of games of DX10 there is 2 groups the group were the use of DX10 gives some sort of visible difference and the group were well...it looks the same as DX9 but runs worse -_-

Games were noticeable DX10 "effects"
Crysis: with DX10 the most predominant effect given is a SH!T load of more blur effects but in my personal opinion I think the blur effect are maybe why too much and while it was suppose to add realism it makes you character look drunk at times it also takes a HUGE hit on the game performance

World in Conflict: DX10 gives you the interactive volumetric smokes (or something like that) that makes smoke or gas react realistically with the environment like Helicopters rotor disperses smoke from burning buildings EXTREMELY realistically this effect is probably the only effect I have found to be DX10 worthy

not games with no visible change
Hellgate: with DX10 you are suppose to get more realistic weather or something of that kind but comparing there is hardly any difference

Universe at War: to be honest it has DX10 support but no explanation of what it improves but I haven't seen any difference at all between the versions

Bioshock: DX10 is suppose to give an extra edge in the graphics by making them sharper but you can hardly tell the difference

as you see DX10 seems to be a hit or miss with some games but what I assure people is that more devs will start forcing more noticeable effects and mark them under DX10 exclusive as a way to push DX10 even when we have read from specialist than most of the current DX10 effect could easily be done in DX9 >.>

The difference between DX9 and DX10 in Hellgate is incredible! I'm using DX9 with graphics on full settings and the game looks like crap, that goes for all others I know using DX9.

DX10 doesn't just change the weather, the character detail is about TWENTY times better. If you need an example go to the Hellgate forums and check out the character threads where people display their characters. If you don't see a difference, there is something very wrong with yer eyes!