I have been using Nuendo for a couple of weeks now (1.5.2), and I would have to say that it is a worthy competitor for PT. It already gives a lot of functionality that PT can't (24bit, Surround mixing, 200 tracks) and it can even use PT hardware if you already bought some. It will take a few years for Nuendo to get it's props from the recording industry, but if you learn it well and use it alot now, you'll be in a great position in years to come. It doesn't hurt that it's a fifth (or less) the price, either! For a host-based DAW, I don't think there's anything that beats Nuendo.