I'm sure streaming is more profitable for them than dealing with physical discs. I'm stoked, if the selection is as good as I hear it is in the US I'll be dropping a lot of my cable channels.
One day in the not-too-distant future, we'll see a headline here "Netflix stops mailing discs to US customers, goes streaming-only." It's (mostly? ideally?) all about the most efficient and user-accepted way to move the bits around.
Netflix (like Amazon with books) has a long way to go before all the movies that are available on DVD are also available on streaming. Also Blu-ray customers would be disappointed unless Netflix can stream in 1080p, which is difficult across a high bandwidth wireless network, let alone the Intranet.
I remember reading somewhere that the reason they called the company Netflix (and not something like, say, Mailflix) was that the distribution model was always intended to be flexible.