RG, I think that everything that you have mentioned might have some impact on your application. However, I want to point out a few points that I came to know from my adviser and one of the friends (I don't know in other univs but in my univ some programs have some graduate students on their admission committee). If you are an international applicant (international means that you are applying from outside US. If you apply from within the US, you are considered as a domestic applicant) then they really don't care about your recommendation letter, but they focus on your GPA, GRE score and most importantly your Statement of Purpose. Yes of course if you have research experience then that would be great. Other things that you have mentioned (experiences during undergraduate such as being a RA, TA, presidents of organizations) will obviously support your application, but if you don't have then it doesn't matter. However, if you are a domestic applicant then they emphasize on the recommendation letters, in fact, in this year's selection one undergrad from our university got rejected simply because the professor under whom she did research did not recommend well. But if you have a good recommendation then that will compensate lower GRE scores. And in some cases if you have research experience then you might have a good chance of being admitted, because universities also want diversities. When I came here and compared my scores with the Indians and Chinese, they were way lower than their, but I realized that because I was a Nepali I got chance otherwise had I been an Indian or Chinese, my application wouldn't have been accepted. Indians and Chinese have GRE scores 1450 to 1500 and TOEFL 290+ (in CBT). That is my experience. Other guys might have different experience. Hope this helps. If you decide to apply in Michigan, then let me know.

Sparty