we had issues getting the press excited at launch. We built a fantastic Windows client. 3 years ago, everyone was running Windows. We were so excited to show the press, yet they all had Macs. Walt Mossberg wouldn't write about our product because it was PC only. Months after we hired our PR agency, we found out that they had never even used our product... because they too only had Macs. It's pretty hard to pitch a service when you haven't used it.*
I'm surprised: I could see a fantastic Windows client being okay before 2004 or so (this might be because I got a PowerBook in 2004, but roll with it). By three years ago the return of the Mac was obvious to pretty much everybody, especially people who care about computing. The people who're running tech blogs, writing forum posts, and so on are disproportionately Mac users.
(http://www.quora.com/Dropbox/Why-is-Dropbox-more-popular-tha...)