I've had a 15" 1st gen MBP, 1st gen 13" MBA, 2nd gen 13" MBP, 2nd gen 13" MBA, 15" rMBP, 11" MBA ,13" rMBP and recently got a 12" rMB, in that order.
Most recent ones all maxed out models spec-wise, with the exception of my new rMB, as I thought I'd end up wardrobing it for a couple of weeks and then return it.
After testing it for some time though, I completely changed my mind. It was the ultra-portable Mac experience I always wanted, which never quite got delivered with the 11" MBA.
Being always on the go, I really wanted to like the 11" MBA, but in my experience, though small, it still weighted more than I would have liked, the screen resolution out of 2006 made my eyes cringe constantly, the enormous bezels were unsightly at best, and the very small trackpad constrained.
The 16:9 aspect ration wasn't that great either, with extremely little vertical screen real estate.
All those things put together, made it a real step back in terms of productivity, from the 15" rMBP I was using at the time.
So I compromised in portability, and got a 13" rMBP a couple of months later, which was the best of both worlds, though heavier and bulkier than I would have liked.
The 12" rMB, on the other hand, is everything I have ever wished for in a portable computer, and more. The keyboard, despite what most say, is the fastest and most tactile Macbook keyboard I've typed on, and after 48 hours of getting it, I was already typing faster than on my rMBP.
Granted though I have been touch-typing for years, and on a desktop keyboard with good switches, I average in the low 100s WPM.
The touchpad is also full size, in contrast with the 11" MBA, which makes a huge difference in productivity, for someone like me who uses lots of gestures. Force touch is really nifty too! Now that I've gotten used to it, the old touchpad feels dull in comparison.
As for the speaker, I was really blown away. It delivers 15" rMBP-like performance, perhaps even slightly better and louder. Sure, there isn't much bass to talk about, but that's to be expected with a speaker module so small. Still quite the engineering marvel considered the size.
Finally, I also really enjoy that they went with USB-C, I love being able to connect power,mouse,keyboard,ethernet,external drives and so forth with just a single cable. It's a brilliant machine for docking.
Sure, you'll have to get some adapters, new flashdrives and cables, but then again that's gonna be the case anyway for everyone a few years from now, so might as well get started on early.
And while I agree that having had two C ports would have been useful, having just one is not a deal braker by any means.
I was also really worried by the Core M, coming from an i7, and hearing what all the reviewers said, but in my experience it's been optimized so well, that I am almost never reminded of being on a mobile processor.
Even running 2 VMs on VMware works smoothly as butter, whilst also having plenty of other apps open on other desktops.
Lightroom with 24mb Raw files in batches is somewhat slower than on my rMBP, but still workable.
Driving a 4K display at 30Hz is perfectly doable, though 30Hz may be a bit low for some uses.
60FPS 1080p video playback works without any issues at all.
30FPS 4K video playback slows it down a bit, but it can still play smoothly enough depending on the compression/bitrate/codec.
If I really have to do some heavy lifting work, I just fire up SSH or VNC, and connect to my 24 Core Xeon server with 96GB of RAM and PCIe SSD storage, and get done with it in a few minutes. But that's what I would have done anyway even with the maxed out rMBP 15", so no change there really.
As a side note, like other reviews have mentioned, I also really like that it can be charged off a standard external power bank with high-enough amps.
This is really a game changer for the frequent travelers and always on-the-go people as though external batteries for the older Macs were also available, they weighted tons, costed hundreds of dollars, and worked sub-optimally.
With this, it can now effectively be run off-the-grid for days with a decent power bank.
So all in all, best portable machine I have ever had among all the Macs I've owned over the last 10 years. All I wished for on a true-ulraportable machine. Sure, it has its limits processing-power wise, but for me the pros far outweigh the cons, and I am yet to find anything that doesn't run as smoothly as on my rMBP for every-day usage. Granted though, I don't do much resource-intensive work locally.
My rMBP 13" is now up for sale. Though I have always gone back and forth between powerful and portable laptops with every new one, I think that technology has come such a way, that I will only get the portable ones onwards.
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TL;DR
Awesome Mac, best I have ever had, bar none, compared to all portable Macs I have had since 2006.
All I ever wished for in a portable machine. Less powerful on paper, but perfectly fine for my every day use.
So light and thin I have to physically open my backpack/briefcase and look to check if I have it with me before leaving. A joy to carry around. Dream docking-machine connecting all peripherals with a single cable.
Love being able to charge it off a power bank, meaning that it can effectively be taken off-the-grid for days with any decent one.
