I'm really liking mine so far. I've been using it for both work and home.
There are only two real complaints that I have about it. The first is that the battery life isn't that great. If you use it occasionally throughout the day you won't have a problem, but you definitely won't be able to make it through a full eight hours without plugging it in. The battery life isn't terrible; I'd guesstimate 5-6 hours on average, depending on how you use it.
The second complaint is that HiDPI is pretty icky on Windows. It's not really an issue with the hardware, but it's annoying nonetheless. If an application isn't HiDPI aware, it'll render the window at normal resolution and scale it up, resulting in some really obnoxious blurring.
If the application is HiDPI aware but they do it in a half-assed fashion (and yeah, this isn't even a Microsoft issue, but it's still important to know), you run into other issues. Regarding Adobe applications, the Creative Cloud application draws everything at 100% scaling, causing the text in the window to appear tiny (bear in mind that the Surface Pro 3 has a 12" display at 2160x1440). Photoshop only supports either 100% or 200% UI scaling, so everything is either tiny or way too large (no doubt because they only intended that to be used with Apple Retina or 4K displays).
The positives definitely outweigh the negatives (and, once again, the negatives aren't all on Microsoft here). It's great being able to seamlessly tap the screen, write on it with the stylus, and even sling the Type Cover out and using the keyboard and trackpad. Speaking of the trackpad, it's surprisingly good for its size, probably one of the best ones I've used on a Windows system. I wouldn't say it beats an Apple trackpad (mostly because of how tiny it is, not its precision) but it's very close.
I'm sure I'll probably post more about it as I use it more, and I'll doubtlessly gripe about it on Twitter at some point, because that's kinda what I do.
