First, streaming video content. After that, streaming video content. After that streaming video content. Oh, yeah...then comes streaming audio content. You may find that downloading apps can have a minor impact, but only if they are numerous and very large. (I downloaded a 1.8 gig map application the other day that took about an hour, but that is very, very rare.)
Unless you have an extremely limited data plan (the most limited available from your carrier), everything else is a nit.