I just got the high end 15" in Space Gray to try out. Beautiful device but I'm not finding the compelling advantage over the late 2013 15" rMBP with dGPU I currently own for the cost. Figured if I did like the new one, I can get more for my current computer selling it on eBay now instead of waiting another year or two to help offset the cost of it.
Here are my thoughts:
Speed - I don't do high end video editing or other things that can tax a CPU so I didn't see a big difference in speed for my usual tasks between the 2 computers.
Touch Bar - it's a nice idea but not worth the increase in price over the regular Function keys. In fact, the TB is actually less efficient in that you have to tap what you want to change then move finger over to slider to affect it (ex: brightness and volume) as opposed to just tapping the function key up or down. Need more apps that really take advantage of it to make the TB a compelling factor and that will take time.
Keyboard/Trackpad - the keyboard hasn't been that big of deal for me to get used to....what's been more difficult to get used to is the size of the trackpad and having palms rest on it while typing. Palm recognition has been fine but still feels weird to have palms on it while typing. Additionally found I needed to change the way I used the secondary click with it - usually go with tapping lower right side but that seemed to impact a regular tap. Switched to a 2 finger tap for secondary click. Making such a huge trackpad seems overkill to me.
The display is beautiful but not finding it much different than my current rMBP. Pro photographers may see a difference in photos but I don't have that discerning of an eye. I use my computer as a 2nd monitor hooked up to the main Apple Thunderbolt display so much more time is spent looking at that instead of my laptop's display anyways.
Add the cost of the extra USB-C dongles (even though they're on sale now) and it's hard to justify the total cost for me. Will give it a few more days but looking like I'll return within the 14 day window. Besides...it's Xmas time and this time of the year is already expensive enough, right?