I've been using an Asus Transformer Book for just over a month now and, while it's not exactly what I was looking for, it's the closest thing to a perfect portable for me, it's still a compromise. Of course a portable PC is always a compromise, and it's definitely closer to ideal (for my purposes) than anything ever made for Win7.
That sort of sums up most of my advice for buying a Win8 tablet. You have a lot of flexibility to pick a device that's the best compromise for you. The cost may be significantly more time spent comparison shopping. I spent several hours comparison shopping, several more hours deciding what was or wasn't a deal breaker, and then back to the shopping until I ended up with something I actually dismissed out of hand initially.
Here's one thing that's certain. By getting a Win8 tablet you are settling for a portable, rather than mobile, device. Despite all the gains from re-engineering Windows to be more modular a la *nix, Windows 8 is still not capable of the energy efficiency you expect from a mobile device.
My 10 inch, Atom powered, tablet has great battery life for a relatively capable laptop. Definitely not acceptable if I were planning to leave it running for hours (even with the display off) between uses. Higher resolution displays and desktop processors are likely to bring that down to Earth. I suspect the combination would drag it down to good, but not great, for a mid-tier (performance-wise) laptop.
The keyboard dock is, frankly, lower quality than any standard laptop I've ever used. The touchpad buttons are crap because of being integrated into the pad. OTOH the additional Asus software provides interesting and useful gestures support. It also adds 500GB of storage and a USB 3 port.
I almost bought a HP, mostly because the quality of the dock - especially the dock connector - is higher quality, but also because I could have doubled the 2GB of RAM I ended up with. I'm sure I'll miss the RAM from time to time, but it hasn't happened yet. In the end, HP's price (I would have paid $100 - $200 more) and lack of a supplemental hard drive were the deciding factors. Keep in mind, though, that's comparing an Asus refurb to a new HP. Otherwise there wouldn't be much difference.
If you are going for one of the mega tablets, definitely give the Surface 3 a hard look. We need a better word for that. It's hard for me to even call them a tablet at all. Maybe slabtop would be a more accurate designation...
At any rate, I haven't used any generation of Surface Pro (or RT - but who really cares?), but my brother used one for a couple months when they first came out. He does ultra high level support for a multinational financial company; tech support for the admins really. His department uses it for on-call remote access sessions and he had nothing but good things to say about it. He likes the iPad and Logitech keyboard/stand even better on the whole, but he is basically using it as a dumb terminal.
Now that I've probably made things less clear than when you started (what can I say? It's a gift), feel free to pick my brain for whatever turd shaped nuggets of wisdom I may have lying around.