It's my understanding that although some consideration is given to the alma matter of an applicant, that consideration pales in comparison to the emphasis that is put on EC's, numbers, and most importantly MCAT scores (supposedly the 'great equalizer').
As others have noted, schools may fall anywhere on the academic spectrum regardless of their status as Ivy/private/small private/lib arts/Large public/small public. In general though, the most academically challenging schools tend to be the Large publics, lib arts schools, and uber-techs (Caltech, MIT, etc.). Private institutions (including Ivies, surprisingly enough) tend to be much easier on grades, largely because they have alumni considerations to take into account. Successful alums reflect favorably on the schools themselves and increase the chance of future donations by said graduates (I might be full of it on this one, but I can't think of any other explanation for their grade inflation).
If you're looking to boost your GPA with extra classes I'd go with the lesser known, non-research oriented publics. I'm a Wa resident, and as an aside I can personally vouch for the previous poster's comment on UW; it's pretty rough. Anyway, rather than pursuing my post-bach at UW, I'm going for either Western or Central U, the reason being that the faculty at these types of schools aren't there to research, they're there to teach. Also, competition at the lesser publics tends to be much lower than at the flagship state schools...
