I consider myself an Apple fan. I love Apple. I recently converted from Windows to a MBA and am not looking back (although I do have Win7 loaded in Bootcamp).
However, it burns me to no end when I receive an email from someone asking for a file, say my resume or a spreadsheet, and I can't just hit reply, hit an attach button, and attach a file. Such a basic function is beyond the capability of iOS. I have to close the email, open up OpenOffice, find the file, and email it to the person, losing all the email trail in the process. And God forbid I need to send a file AND a picture. I am screwed. Two emails are needed for THAT.
I think we are far enough along the iOS development cycle that some solution to this should be forthcoming. In the meantime, I grab my Galaxy Tab, fire up GMail, hit reply, hit attach, and attach to my hearts content.