Flash is a vector animation (read about vector animation software) software, originally designed to create animations for display on web pages. Vector graphics are ideal for the web because they are so lightweight.

Flash pages can be made to load faster, but most of the time, the way they are designed in the real world, they do not. That is not a Flash problem, it is more an issue of the Flash developers going nuts with fancy and heavy Flash movies.

Flash handles text very poorly. The web for the most part is about text, we go to the web to read about things, whether it be articles like this one, or what is in your shopping cart, or the latest baseball stats, it is all text.

Flash text rendering/displaying is much slower than HTML and noticeably less clear. Macromedia knows this and that’s why they include the ability to display basic HTML in Flash and that’s why on their own site, they make heavy use of  HTML.

You can do some really nice work in Flash that would be difficult and sometimes impossible in HTML alone.

I see Flash being used selectively to enhance an HTML based site.

These are examples of FLASH animations (like little commercials):