With Apple and Adobe at each others throats lately over supporting Flash, there has been considerable debate over the usefulness and necessity of Flash. Critics of Flash cite its poor performance on certain platforms, its poor index-ability and its future replacement as a video platform by HTML5. Lets clear a couple of things up.
First, I think the reason Flash gets such a bad rap is not due to Flash being bad, but a lot of people who are using Flash being bad at it. There are a number of sites who use Flash or Flash-based technology, and it works out just fine for them.
For example: Chatroulette.com
This site is presumably built on a Flex platform, and while it may not be the most stable web app in the world, consider what its doing. Its a two way video chat thats randomized and basically is transferring an enormous amount of data. When your capable of doing that with HTML5 you let me know.
As for the complaint about Flash not indexing correctly on Google, that is the responsibility of the web developer. You should make sure your flash is embedded properly, and the Flash should fall back onto an HTML page in the event that flash is not supported . Also, your Flash shouldn't all be on one URL, that kills "back" button functionality, and pages do not index separately.
I think Flash's handling of video content delivery is outstanding. It's a shame its not supported on mobile platforms or "iPads", but for whats it is supposed to do, it works. I have to be honest with you guys, I am not blown away by HTML5's video handling. You can kiss your custom video delivery systems goodbye, and everyone will have the same video display format. Not my cup of tea.
I think the worst thing Flash has going for it, is it's tendency for it to fall into the hands of inexperienced developers. This situation is a breeding ground for things like horrible Flash intro's, overdone Flash navigation, and time consuming animations that aren't even that visually impressive.
My final point being, Flash has its time and place. Its not as horrible of a technology as people make it out to be. Granted, I wouldn't build a blog in Flash, but you can be sure that had they wanted a custom video display for blog posts, it would be done in Flash. Sites that depend upon being interactive and rich, like restaurants, nightclubs, etc.. all benefit from using flash. Sites that are content and data heavy such as blogs or forums shouldn't be written in Flash.
Bottom line, it's not what platform you use, but how you use it.