I agree, doom was in a small box and still laggy. HL2 is great!

a unified lighting engine takes a LOT of horsepower, deus ex:IW is another example nearly, it wasn't doing half as much as doom3, and runs about 300 times worse. HL2 is making the best of all the old tricks, plus a few new ones that dx9 parts should have no problems with really (is hdr even on by default on high end rigs tho?) and HL2 is directX, and doom3 is openGL, and ATI REALLY suck at openGL still.