lack of apps are still a big problem for WP. Yes some big name apps like Whatsapp are available. But many BIG corporations/enterprises/company like bank, insurance company, TV stations... just don't support it. For many if they can't use the phone for mobile banking, work with company apps, watch TV... it is just an useless smart phone. These kinds of WP app support outside of North America are even less popular (WP/WM support is nonexistent in most Asian countries). MS still have a LONG way to go.
corporation/company that don't support WP:
HBO, Bank of America, Chase, JP Morgan, Morgan Stanley, TD Ameritrade, Bank of Nova Socita (Canada), HSBC (UK/HK), Mitsubishi UFJ Financial Group (biggest bank in Japan)...