first of all, congratulations.
now, it definitely depends a lot on how you'd feel if something bad happened and you had stuff already bought. so, what applies to one person definitely doesn't apply to another.
on my side, i'm currently 12w+5 and all's good so far. in fact, i started buying a few things even before i was pregnant, because knew i wanted a baby (was willing to adopt if we couldn't have one).
after i got pregnant, i was dead scared i'd get some horrible news at the 12 week scan (although i knew chances were everything would be fine). but decided that if i'd had a miscarriage or other problem, i could always use the stuff i'd bought for a future pregnancy. i just kept them all in boxes in the cellar, so they wouldn't be very visible.
again, that's only my own personal experience. but, as a sidenote and possibly useful to all of us stressing out over nothing: there's a VERY HIGH probability that everything will be alright. really!
and again, congratulations!