Net Entertainment has build a download client in which their flash games can be played. I think this is a great alternative to playing on a gaming portal. If I just want to play casino games then I think a download client gives a better player experience.
Adobe AIR is also great because you can incorporate flash, html and other formats in the client, and you can make the client much more than just a download client like all the rest on the market. You could add different widgets and make the player experience even better.