Not to dismiss the problems you have encountered, but I too use dropbox heavily with 100k+ files. Not as much as you do but still quite a bit more than the average user.
I had tried out other common services (Google Drive, Skydrive) and they all choked with that large of a file collection. Skydrive would just crash and exit whereas Google drive had issues with file uploads. And both of these had terrible CPU usage (it was basically at 100%) which is not good for a laptop. This was a couple of months ago, so may be their syncing client have improved since then to deal with large file collections.
Dropbox on the other hand was the only one able to handle my humongous file collection with no sweat. But as you point out it too has its limits. It's good to know that once one gets past/at 300k+ files, there are likely to be issues. I agree with you it will be good for Dropbox to publicly acknowledge the true limits they have in their service.
I had tried out other common services (Google Drive, Skydrive) and they all choked with that large of a file collection. Skydrive would just crash and exit whereas Google drive had issues with file uploads. And both of these had terrible CPU usage (it was basically at 100%) which is not good for a laptop. This was a couple of months ago, so may be their syncing client have improved since then to deal with large file collections.
Dropbox on the other hand was the only one able to handle my humongous file collection with no sweat. But as you point out it too has its limits. It's good to know that once one gets past/at 300k+ files, there are likely to be issues. I agree with you it will be good for Dropbox to publicly acknowledge the true limits they have in their service.