I saw the Surface Pro for the first time today at Best Buy. They had the RT and Pro side by side so I was able to really do direct comparison. The Pro was about as thick as I imagined, not that bad, but it was heavier than I anticipated and made the RT feel petite. The Pro felt good and solid but I wouldn't want to hold it up in one hand for an extended time. Both screens looked great and the distinction between the two models is not dramatic. It reminds me of the iPad 2 and iPad 3 where my friend and I were not sure which was display was Retina without looking closely. The dramatic and unexpected difference was in speed. The Pro flies through web pages and apps compared to the RT. Having them side by side and hitting each screen at the same time... major difference. I hadn't really considered getting the Pro but seeing it in action was persuasive. If it wasn't for the 4 hour battery life the decision would be easy.
BTW, the salesperson at Best Buy knew details about both Surface models. He said he wanted the Pro.