The USB-C is what worries me about this otherwise great MacBook Pro update. If it only has USB-C, no less than five standards (MagSafe, USB-A, HDMI, Mini DisplayPort/Thunderbolt 2, SD card slot) are being dropped all at once. Many people (myself included) who use these Macs aren't ready for that yet.
It's going to suck for anyone who actually uses any of the ports on their computers (I assume most MacBook Pro users do). There is no other option than to buy the expensive adapter and work through that. So pretty much the only thing you will ever plug into your MacBook Pro will be the adapter, and everything will go through that. Then by the time every non-USB-C product you own has gone obsolete and been replaced, your computer will have gone obsolete too anyway, so you'll never have benefitted from the USB-C ports.
The thing is, if you buy a top of the line, brand new Mac today, it will come with regular USB ports, with the exception of the MacBook which I wouldn't really call a worthy example of what a computer is supposed to be. Due to this, most accessories will also come with regular USB ports until the day most new computers come with USB-C. That day has not come yet. And when it does come, it will take years before USB-C becomes widely adopted. So I think it's safe to say that any computer that only has USB-C ports today is at a major disadvantage for its entire useful life.
Of course USB-C is great, it's literally one type of port to replace all ports, finally, we've been wanting this for a long time. But Apple always likes to adopt things before everyone else does, which is why early Apple adopters never get to enjoy their early adoptions. This is not an issue if we just wait it out though.
I'd say
never buy a first generation Apple product: it costs more, it's incompatible with current tech, it has unnecessary limitations (only 1 USB port on first MacBook Air and current MacBook, no 3G on first iPhone, etc) and it's untested so will probably fail a lot more (first retina MBPs had lots of display issues). The 2nd or 3rd gen will be cheaper, better tested, and by then the tech will have become more widespread and compatible. But for this to happen, the 1st gen has to come out, people have to buy it, etc... Just don't be those people.