After many years out of Flash and inside HTML5, I can dictate: nightmare.
It’s a world of possibilities but, regarding developers, a totally *ucking nightmare.
100% of customers think they need support for desktop computers and mobiles devices. This means a minimum of Chrome, IE, Firefox and Safari, in different environments (desktop, tablet, mobile) and OS’s (Win, Mac, iOS, Android, including Win 7 thru 10, Mac 10 thru 12, iOS 8 thru 11…), and usually as well the customer’s frontend app, which uses to be a Cordova-based app (also available for iOS, Android and desktop Win and Mac).
Regarding audio and video, you stick with mp3/ogg and mp4/ogv. Regarding programming, you rely mostly in general-use libraries such as jQuery. For the rest of functions, you create your own libraries, aimed to support around 40-50 different browsers/versions.
In the end, you spend in development a similar amount of time than you spent previously in Flash (mostly because Flash is still available for impossible tasks out of Flash, such as RAD —standing for Rapid Animation Development, instead of Application—, now with HTML5 output thanks to CreateJS).
But some times you spend around 100 thru 200% of the time with debugging tasks. The last time I had a bug in the customer’s iOS app. The code worked fine in the other 40-50 browsers, but not here. I had to re-make at home the app and simulate the customer’s code in order to replicate and debug the issue. This converted a simple 2-hours job into a complex 4-days job.
My advice to all my customers all this time is the following: force your users to use your own app. This way you develop and mantain 1 code.
Otherwise, take care of your problems. No! Your supported browser’s problems! The transition from IE10 to IE11 caused an issue which affected to almost 1000+ interactives to one of my customers. This customer had the luck to have my company as the responsible of such interactives, as we managed to resolve the issue quickly. However, this issue caused a bunch of negative comments in the different app stores. This is because my customer lets the browsers decide which work and which doesn’t, how and when.
Flash movies worked the same all around the browsers and operative systems: 1 code, 1 behavior.
This is just the first round. I wanna tell you more about this!