I'm sure the majority of Surface Pro owners will say it's worth it. It all depends on your needs and what you intend to do with it. If you want to run ANY windows program(s) (like on a desktop PC or laptop) you will have to buy the Pro. If you are content with just web surfing, emails, applications, and light office work I'd highly recommend the RT over the Nexus. Like apoc said the Pro and Nexus 7 are two very different devices. The Nexus is similar to the Surface RT. You can compare the Pro and RT here: Which Surface is right for you? - SKU Chooser
You should consider the Surface Pro as an Ultrabook/laptop in tablet form-factor, you can do anything on it that you would be able to do on a laptop or desktop with similar specs (i5 dual core processor and HD4000 graphics and full windows OS) with the bonus of touch screen, digitizer pen, and small form factor for portability. The Nexus 7 is more like an iPad or windows RT device. It gets better battery life (and note that the Nexus 7 will have a smaller form factor and smaller screen real-estate) but you cannot use it as a computer for anything other than what the Android app store provides, so if you need an app or program not in the app store your most likely SOL.