I hope not, I only have 1/3 in, but Wake Forest did send me an email telling me if I don't have the other 2 in by October 15th my application will not be considered soooo...

Yeah got that same email from wake

I don't know the answer to this, but if the MSPE's aren't available until Oct. 1st, isn't this as much a hold-up as having pending LOR's? In other words, I guessed that programs might be waiting on MSPE's to make decisions re: interviews. Is this a reasonable thought process? I got that e-mail from Wake as well.

This may now be more apparent but I just assume you should go by the individual programs stated deadline. They vary quite a bit with some in mid November and others earlier like Oct 15th for Wake Forest. Obviously this puts different schools before and after release of MSPE letters. Regardless, if everything that particular school wants (aside from MSPE) is not in by that date I think it's safe to assume it will hinder your chances for an interview. I certainly do not claim to know if/how/which schools offer interviews without the MSPE. Honestly I appreciate Wake Forest sending out notifications and I hope others do the same. It lets you know you are not (or are) missing anything.

Absolutely not. You can add letters as they come. In fact, programs expect this. I did mine intermittently as they trickled in (in fact, some of mine didn't get in until the big deadline dates (i.e. 10/15, 10/31, etc...)) and didn't seem to make a bit of difference. Letters are important, but I feel they aren't too helpful in the initial screening process. I think once a program has whittled down the applicants, then individual letters may start to make more of a difference. Heck, I know people who got interviews without having any letters uploaded at all. Don't sweat it.

Good to know as I have been getting stressed about getting my letters in especially with deans letter going out tomorrow, was afraid it might hurt my chances of getting those early invites.