Google may treat the .co equaly as com.
But apparently the .CO-REGISTRY DOESN'T treat .CO as .COM. in 2 ways =

1/Pricing is triple time as much (!) as .com-domains.
This counts also for renewals.
If the .co-registry diminishes the pricing, then maybe they get even with .com, (or are it the registrars who ask much much more to get more profit ?)

2/If the CO-registry would allow French "ô" IDN's Internationalised Domain Names, and IDN's of several other languages, f.i "ù" (Italian), Korean, Chinese, Cyrillic (Russia), THEN THEY CAN SAY their target is the WHOLE WORLD. At the least they should allow VERY SOON French, German, and other characters like ù, ç, etc.... Korean, Chinese could follow later.
But NOW only SPANISH IDN-characters are sustained !

3/Several CO-Premiums are not released yet and will be auctioned ...at a time in the future. NOW WE SEE THAT ONLY 100 domains of the auctions of last year are reauctioned.
Are they going to wait 5 years or more, like dotmobi that still has 4.000 or more premium domains that aren't yet aucioned or allocated to developers ?
Don't wait too long with the Premiums !

4/.CO has to HURRY. In preregistrations of a registrar that already allow preregistrations, of the new TLDs the most preregistrations are for ".web".
Those new extensions will only come in 2013, and maybe even only at the end of it. But they are coming.
.CO has 1 OR 1 and a half year, to become popular, before those newtlds are coming.
The MOST IMPORTANT THING that will make or break a new TLD is the PRICING. If new TLD's ask MORE MONEY then .COM (like .XXX does now asking 80 USD or more for 1 domain), it won't be a succes if they keep the high pricing, certainly for renewals.
Look at the example of .CM of Camerooon, of which was said that it also resembles .COM and gives type-ins due to errors, who ask 100 USD or more for 1 year registration. Who talks now still about .CM ? Nobody. But at the release registrars gained a lot of money, as it was also (partly/mostly) advertiseded and released as "the new .com". I have to admit, .CO has probably more success then .CM already. And the reason is the pricing, and the fact that .CO resembles .COM more then .CM.

Peter, don't lie to yourself...things change. The extension is barely a year old...how are the top keywords going to rank when they are still in development? You must be a .com domainer afraid of your domains losing their exclusivity and, therefore, value. There are so many .co's in development right now where the .com is parked because the owner thought it was worth a zillion dollars. This is why .co is a great alternative...it's affordable and, almost anywhere in the world, it means company. Check out Faust Brewing...they use the .co for their site even though they have the .com...imagine! Aren't they afraid people will think they are a Colombian company? Ha! This is but one of several examples I have found where the owner has both but chooses the .co. It makes sense. I'm sure .com will still retain it's dominance for years but in 10 years? not so sure.

Have you ever saw a .co website on the 1st page of google for almost any keywords? no.So don't lie to yourself.only .com will make the mark.