Size wise, I think it's been designed perfectly. In it's box when purchasing in store I thought it looked smaller than I had anticipated. When unboxed and before first switch on I thought that the proportions looked good. Powered up and went through the set up procedure and on first use it felt spot on.
Going on the Apple event presentation I had formed the impression that the pro was going to be larger than it actually has turned out to be. That's not to say that I am disappointed, far from it, I'm coming from the last of the pre-air iPads which I find is still perfectly usable even with ios9, and holding each device in a different hand the pro is lighter so will still be perfect for evening armchair use (a question raised by a previous poster).
Apple use the word "ginormous". We all knew it was going to be a much bigger iPad, I just found it difficult to visualise before I saw it, but on use it is ideal for what me and my eldest intend for it which is to try it as a Wacom replacement for my hobbyist art and her hopefully higher level creative work and, occasionally, to use for more enjoyable media consumption. Ginormous was just a marketing word which is fine, but the device seems to sit perfectly for our intended use and, I imagine, for many others. It's not too big and it's not too small. It's just right.
Initial impressions are that it is lighter than expected for it's size and lighter than my pre-air pad which I use comfortably most evenings, has a beautiful display, runs very fast and smooth, handles the Adobe cc apps and other creative apps extremely well so far. I expected all of the latter otherwise it would have been a failure out of the box, but the low weight/size ratio of the device, in use, has exceeded expectation.
Other than the confused launch and shortage of first party accessories, my humble opinion is that Apple have delivered a great product and one that meets, and might exceed, my expectations. Budget aside, I think that it is a product that will delight casual and content consumer users as well as creative users, at least at my daughter and my own current non-professional levels. I will be interested to learn what professionals eventually make of it as an additional tool.
Don't get me wrong, I did say budget aside, and although I hugely enjoy many Apple products it is hard to ignore some of the cynical product marketing decisions across the range and I am no slave to the brand, but if you can live with the UK premium pricing then this is a product that I don't think will disappoint.
It won't replace our iMacs and our MacBooks and, of course, it isn't an iPhone, I don't need it to run OS X (which it was never going to do in this iteration) so it seems that Apple have found a perfect space for it in the product range. What a surprise!