I've only recently got Black Ops and love it, purely for online play and zombies.
MW3 sneak-preview trailer is out, for anyone who's interested, and hasnt seen already:
Call of Duty: Modern Warfare 3 - GAME.co.uk
And 3 'In Game' Screenshots here:
Call of Duty: Modern Warfare 3 screenshots released | T3 magazine
If you are in the UK, cheapest places I've seen to pre-order are Overclockers.co.uk and Sainsburys. Both offering it at £35.99 (Inc. VAT). The rest are pitching it between £40-£45.
Looks a bit tasty, but then again, I suppose any Call of Duty game would do, wouldn't it?