The web and desktop email apps arena is a crowded market, but none have done it well IMO. The good desktop apps don't offer web or mobile (Mailbird, Thunderbird, Mailspring, eM.)
The existing web clients (Gmail, Outlook, Yahoo) don't do well at all in offering support for multiple account aggregation across different providers.
Most of the great mobile clients (AquaMail, Mailwise, Nine, Blue, EasilyDo, Astro) don't have desktop or web apps. The few who do/did have desktop or web apps are not quite as great on mobile (Missive, Moo.do, Flow-E), charge too much (Newton) or have been discontinued (Alto.)
Probably not much money in it, but sure would be interesting to see a web-based AquaMail. For now, I use Wavebox to bring everything together and occassionally MissiveApp.
In regards to the new speediness: Opening emails, the loading times were remarkably faster. I always load images automatically from recognized addresses and typically this can take a few seconds. Today the emails loaded almost instantly. I have noticed a little slow down in the past hour, but still speedier, so who knows.