Gruber mostly blames the App Store economy for the failure of Vesper.
The market for paid productivity apps for iOS is simply too difficult.
However, I don't think that is the root cause here. Here are my thoughts on why it failed:
1. Limited to iPhone
There is no way a 'Notes' app that limited your data to the phone was ever going to be successful.
As an Evernote user, I remember looking at it and deciding against buying it because I couldn't access my notes on my desktop. Heck, I enter most of my notes data of my desktop and only use my iPhone to view it.
Gruber alludes to this himself a little in his blog post:
A notes app is only of interest to many people if it’s available both on their desktop and mobile device. The number one reason, by a long shot, that people didn’t buy Vesper is because it wasn’t available for the Mac.
The entire post doesn't even mention Windows or Android. Windows is used by a huge number of iPhone users. Also you always think in the back of your head that if you ever decide to switch to Android, you don't want to lose your data.
2. Not differentiated enough
The only thing Vesper had going for it was the fast and clean interface.
However, this seemed to come about due to its lack of features, not despite of it.
Evernote, for example, has to:
- keep your notes list in sync all the time
- account for sync while you are typing
- allow formatting of text
- allow server side searching of text
- download and generate previews of image from servers
- allow attaching pdf and voice memos to notes
Vesper's sync is really just a backup service. It doesn't have to deal with all the complexity of a fully sync enabled notes app.
The fact that Vesper doesn't have most of the features above really makes it useful for very casual uses like creating grocery checklists, only it doesn't even have a 'checklist' feature...
3. Evolution of native 'Notes' app
All this while, the native iOS 'Notes' app evolved. It is fast, syncs with iCloud, and has more features than Vesper like Checklists. As of today, there is no real reason to choose Vesper over iOS Notes.
Its easy to blame the App Store for your failure. However, as is often the case, the fault lies with the product not the market. If you are selling Notepad when your competitors are selling Word, its hard to see how that would result in long term success rather than just an initial spike of curious users.