Tessellation is subtle but does remove edges and rounds off items. I also personally really like DOF in this game and it did add to the overall experience. I think its a great effect.
Obviously these both place a big hit on frames, but if your rig can handle it then it would be crazy to turn it off.
What DOF tries to do, is give a peripheral vision effect, nothings quite in focus except the middle of the screen, unfortunately the problem is in real life you can move your head(which the game tries to emulate) or your eyes independantly of your head, which the game can't simulate at all, thereby creating a completely unrealistic and daft effect.
Huge effect to add realism that kills performance, and is less realistic, the effect itself, is incredibly basic, slightly fuzzy/blurry, wooooo.
Its like the truly awful physx implementation in Mafia 2, huge power hog to supposedly give us better and heres the kicker, MORE REALISTIC effects, however most of the effects are less realistic, but try to be flashier, and it fails miserably, glass "exploding" effects in that game have a minor delay before it happens and each piece of glass explodes in a circle, perfect circle, with bits that don't really look like glass and don't take into account the bullets angle or direction(ie bullet goes through glass, glass should shatter and fall mostly in the direction the bullet was travelling, bad new effect, glass shatters equally in all directions).
DOF isn't realistic, and personally I despise having any part of the screen blurred out in an unrealistic way, full stop, when it takes a huge amount of power to generate an unrealistic effect thats less realistic than simply not having it on, its a truly crap effect.
One of the key problems is, for instance the clipboard, it comes up in the corner, with DOF off, the whole thing is clear, with it on, its blurry, its just completely daft.
Depth of field/peripheral vision type effects, until we have monitors with ickle accurate camera's that track our eye movements and unblur exactly where we are looking, they'll be rather pointless effects. The other issue being, by the time we have that kind of eye tracking stuff as standard, I want me a ruddy holodeck to go with it.
With tesselation, its pointless its a VERY marginal change which you only notice when you really look for it. Changing between high and low res textures effects every pixel on your screen all the time, the difference is night and day, I can see the difference mid insanely intense battle, and while walking along slowly looking at things, Tesselation I can't notice, AT ALL, while in battle, or playign 99.9% of the game, until I stop and stare at really only some very specific items, you don't notice it. Considering the top end cards will run sub 30fps average with DOF/Tesselation on, theres really very little reason to have them on, if I've paid £700+ for 480gtx SLI, I'd prefer not to be running 50fps average with 20fps lows, by having both on, closer to 100 average with 40-50lows is what I'd expect for £700+, and considering the quality of the effects, I'd never turn them on.
Tesselation isn't that big a killer, DOF hurts performance a good 1.5-2x harder than Tesselation does.
WIthout either on, frankly, those [H] benchmarks are accurate for WITH tesselation, without it add another 10-15fps most likely. I'd expect a 5970 to be averaging WELL above 50fps, if you're getting 20fps, somethings wrong, uninstall drivers and try the 10.4 or 10.5's, guru3d.com(or its 3dguru, always forget) keep a backlog of drivers for download, reinstall with one of those, try a new physx driver, and maybe try installing it twice just incase(seemed to work for Mafia 2 for Nvidia guys).
Then see where you're at.
