As always, AnandTech has the only review of the new Surface 3 that really matters.
So with those caveats aside, we can finally get to the conclusion that you have likely guessed already. The Surface 3 is a great device. The build quality is really at the top level of any OEM out there. The form factor is finally the right one after two previous generations that got it slightly wrong. The weight is lighter than any previous Surface, and just as balanced. Performance of the x7 Atom CPU is great for light tasks, and if you need more than light tasks then this is not the device for you. As a tablet, it is great to use in either orientation, with the portrait mode being especially good now for browsing the web. The kickstand is improved, they keyboard is improved, the base tier steps up to 64 GB of storage, making it actually useful without immediately adding micro SD to the mix.
When I was weighing the pros and cons of the retina MacBook Pro vs. the Surface, I eventually ended up not going with the Surface because of the keyboard and trackpad. As nice as the Surface hardware is, its detachable keyboard and trackpad (whether it’s the Pro or the regular) are several orders of magnitude worse than those on the MacBook Pro, which are best-in-class (well, the trackpad at least). Those are the primary input methods for my kind of use, so the MBP won out in the end.
The point: Microsoft should just make a Surface laptop. Keep the detachable model as well if you want, but also offer a proper Surface laptop that can compete with actual laptops.