the opteka grip, as i've said a thousand times before, is out-freaking-standing for the price. i got the one with the 2 generic batteries, so i have 2 canon batteries, and 2 digi-whatever-brand ones. i couldn't tell you the difference between the batteries, they both last frickin' forever. as far as the grip itself...good lord it'll change the way you shoot. i have one on my XTi and also gripped up my work's 5D and 20D. it only takes a few days to get used to. as a matter of fact, i thought it was just kind of 'meh' at first, as i didn't even realize the scroll wheel and second button on it! after i realized those were there, it occurred to me how important an addition to the camera it was. more power, better flexibility in shooting, better grip, it balances out nicely with my 580 on top of the camera...you can't go wrong for a $70 investment.
for the record, i have the canon grips for the 5D and 20D...you honestly can't tell the difference between the opteka and the canon one. and neither can anyone else 
also, to further thread-jack, i have 3rd party hoods on my 50mm 1.8 & my 85mm 1.8...no one's ever noticed those either..
paying 50 bucks for a freakin lens hood is ridiculous. www.dealextreme.com
has so many awesome 3rd party lens accessories that have saved me a ton of money. it's a chinese site, but they have awesome quality gear.wireless remotes, center-pinch lenscaps, umbrellas, flashes, you name it.
but yes, get the grip. you'll need a bigger bag though.