You can play for real money or work your way up from the free poker games. This allows player actions to be uploaded quicker and each action to transfer smoothly. Although some poker sites are still using outdated Flash-based options to make no download instant play work, it looks like 888 is using lightweight Javascript coding.
Buggy, unresponsive, and finicky about your browser are what I think of when I see Flash.
There's really no download required to get the full playing experience. Chrome, Safari, Edge, and even (gasp in horror) IE. It all transferred and loaded each lobby and real money table within 3-5 seconds. I've tested the 888 Poker no download client from a Windows 10 PC, a Mac, an iPhone 6 Plus, a 3rd Generation iPad, an Android phone, and a cheap Android tablet. Why it's probably the best no download poker site: