I've learnt from experience that there's another warning sign: Silence. If no one is making suggestions, complaining, or promoting your product then it indicates apathy. Which means that you aren't solving a critical problem
What if your product is just not critical? Is that a <i>terrible</i> thing? I can't imagine every application is absolutely critical to an operation. I would argue that most B2Cs and a good percentage of B2Bs are not critical software, but many of them do just fine.
I really wish the author had mentioned the name of the app with the sucky UI. I would love to take a crack at implementing a competing program with an awesome UI so I could completely own that market.
Although solving a critical problems is a significant advantage (especially in the b2b market), I think it is also possible to establish a business based on adding-value or improving upon various aspects of a business or consumer experience. Add-ons to existing products and web apps that simplify a more complicated workflow are good examples.<p>I find that much of the functionality of many successful web apps can be replicated in a spreadsheet, but the added value of the time savings, improved functionality and simplified workflow make the web app worth the price (although not necessarily critical).
The warning signs are people saying "I'd use your product if..."<p>OK, but what if people use and like your product for years, but it still spreads slowly?
This is an interesting blog post because I've noticed that often the apps that solve the most "mission-critical" problems have the worst UIs. Maybe its the complexity of the task as much as lack of effort? I'm not sure. On the other hand the most beautiful UIs are often on top of apps solving extremely trivial problems.