Bubbaap,
From someone who's been there, be concerned about it but don't stress yourself out. Apply to a variety of schools to give yourself more 'padding'. Be prompt with your secondaries. Some schools won't let you do a secondary until your scores come in--don't sweat it, just be prepared to get those secondaries done asap once they send them to you. And you may have to explain why you waited until August in your interviews...
Here's my story: I took the MCAT in August (35Q) and applied to only seven schools (financially I couldn't do more than that, applying to 15-20 schools was out of my league). And I waited until late Aug./early Sept. to submit my AMCAS (I didn't know any better). Knowing I was at a bit of a disadvantage, I sent in most of my secondaries right away, well before the deadline to show I was interested and serious about applying. I ended up withdrawing my application from 3 of the 7, and among the remaining 4 (all of which I interviewed at), I got two rejections and two acceptances. Two of these schools I got immediate responses from after I sent in the secondary, while the other two didn't respond to me for a few months before inviting me to an interview. I was accepted to one school from each group. My impressions of the schools I didn't get into were that my late MCAT made me look 'less serious' about medicine. But I got into the two schools I wanted most, so it didn't bother me much. But I also know that with the few schools I applied to and August MCATs, I am very much the exception to the rule.
My point is, some schools will look at it as a negative, while other schools won't care much as long as you are an otherwise competitive applicant. My advice is to call the schools you're most interested in and ask how much of an impact your 'late' MCAT will have on your application. While all schools will say that they accept August MCATs, some may tell you that the late MCAT takers get their applications reviewed last or after the first round (not a good sign), or they might say they review your application and then hold it pending your scores (a better option, esp. if you have a strong app that makes them interested BEFORE getting your scores).
If you have the ability to apply to a lot of schools, it will definitely make the process easier, and up your chances of getting in somewhere. It IS doable with taking the August MCAT. Med school acceptances can be a bit mysterious, so always be yourself and convince them that they need you. Anyways, this is just my $.02...
smurfette