Make it intuitive, design it beautifully, implement it intelligently – if you do this all of your users, no matter how they access it, will have an incredible experience.
The Promise of Flash
To me, that was always the biggest draw to Flash. At a time when so much energy was going into warring with the various browsers to obtain similar experiences, this platform had managed to propagate across them all and offered a safe haven, a way to ensure the user experience you envisioned was the same no matter how it was accessed.
The results of this was some really engaging experiences, coupled with innovative interaction decisions born out of a freedom from the nuances of the different browsers. TheFWA (http://www.thefwa.com) showcased these on a daily basis, and I can remember beginning to design with experience in mind first, execution second (knowing that Flash would enable it).
The Shadow of Implementation Rises Again
I won’t go through the demise of Flash (here’s one of my favorite infographics on it: http://www.wix.com/blog/2012/07/the-authentic-infographic-history-of-html5/), but once again the thought of implementation began to cast a shadow on the design process. “It’d be perfect if we could have it slide out here….oh wait, that’ll never work in IE” – almost overnight it seemed that all UI decisions were being put against the worst case scenarios in the browsers. Some design progress followed along, larger images, bolder layouts, but always the threat of implementation limitations remained. Menus at the top or left, thank you very much, and be careful with those animations, you could hurt someone.