Well, now that all depends! (I hate that phrase, don't you!)

Actually, there are different reasons for using Flash, but to me the greatest is that it creates a visually stunning/immersive experience for the user.
To define racticality, you have to look at the desired results first.
If your desired results are to quickly display information, or provide a research tool, Flash probably is just a hinderance. If the desire is to provide captivating experience, or a custom interface, (along with many other uses/scenarios) then Flash is definitely a practical, versatile tool.

Thoughts may very on this subject, but those are mine.

Regards,
Jabez