I suggest the New Macbooks (and Pros) will be released Sept. 23 for these reasons (according to other rumors postings):
a) Even lower-level apple employees are already using the new macs
How do you know it? I don't remember any rumors mentioning lower-level employees using new MacBooks...
b) Some people have spotting them (possibly) being loaded into Apple stores already
People often don't see what they don't want to see. The reverse is true as well.
c) Announcement of Android phone on Tuesday (Apple will want to deflate that release)
Deflate the release of a phone by the release of a computer?
d) Release of Iomega eGo Helium product, supposedly for Air, but if you think about it, its really for the new entire line of MacBooks (and Pros) -- note it doesn't say Air in the name of the product. A recent Apple Insider article says "Air seeing decreased demand" -- why would want release a new product for a decreasing market
You're right, it's not named "MacBook Air's perfect drive". It's called "Helium", which doesn't mean Apple will release MacBook Helium to match it. Iomega is not Apple, and I think they were planning to stop supplying third party manufacturers with details for their new products anyway, so there's close to no chance they know anything.
e) Its a Tuesday -- most Apple announcements are on a Tuesday
I've seen some Asian blog a while back that had a calendar consisting only of Tuesdays, for that very reason. This and "Apple" were the only legible (for me) things there

.
f) One other rumor poster said that he has a relative that work there and that customers would have them by the end of september (and hence, need to release them say a week before end of sept.)
I didn't see that post and I've no idea how valid this point is.
g) New nvidia chip information to be used in new mac released.
I've heard MCP7A-U, the one rumored to be used in MacBooks, is to be released on 23rd September, so you *might* have a point here - unless they moved the date once again. It doesn't mean MacBooks will be released simultaneously, even if they use this chip - and it's by no means certain.
h) In the Seth Weintraub blog "Apple Macbook redesign noise reach a fever pitch" says "The October 14th date actually seems far off as a release date now."
It doesn't count as an argument in itself, since he gave the same reason for this conclusion as the ones you've already mentioned.