Would respectfully disagree. Dropbox and Box are building an awesome app platform as well and as long as users want neutral solutions (non iOS or Windows), they should be OK. In fact Box and Dropbox will start specializing as the author noted.
I definitely benefit primarily from Dropbox's neutrality. Much as I benefit from the neutrality of lastpass and xmarks. I can use them at home on the latest Mac and Linux, I can use them on personal VPS instances, I can use them at work, even in a fairly locked down network environment.
iCloud is useless at work, and my officemate has switched from SkyDrive to Dropbox for the same reasons. We now both doubly benefit from the wide-ranging accessability and sharability of Dropbox.
are you confusing neutrality with it being a web app? What part of the above things you could not do with say skydrive?
Basically I don't see a difference between dropbox and skydrive (or gdrive or....) as a developer, if I had to choose, I'd probably choose a platform from a company that has a long history of building platforms (Microsoft or Google or any other big co) as opposed to dropbox which is a tiny startup somewhere with no viable long term life expectancy.
Dropbox has a Linux version. It's not a web app. I've used it in Unity/Gnome/Nautilus. It feels exactly right. It also works perfectly on OS X, Windows, Android and iOS.
When you say neutral solutions, you are assuming that the API developed by Apple and Microsoft can only be accessed from these platforms. I know that that's not true at least for SkyDrive API.
