It also allows you to see all those wonderful ads that were previously blocked. There's a way around that, if you're interested -- open the browser, tap the menu softkey, select more, select settings, then scroll till you see the plug-ins option. Select on-demand, and voila, you only see the Flash you want to.
It's a great addition -- more media, access to a few games that work without too much problem, and once more sites start optimizing for mobile content in their Flash content you'll see a lot more.