Ok - background info. I switched from Windows to Mac years ago. Simply got tired of re-installing every 6 months to keep a clean system, and smoothly running - as well as Vista. I've been a happy Mac user since that time, and still am. I think Windows 10 is ok - it holds some promise, but not ecstatic. After I saw a friend with an SP3, I was pretty impressed with the hardware. Got an SP4 the day they were available retail. Mine has been relatively trouble-free, a few things, but not the major things that so many others seem to have.
As to your questions:
1. Are there any glaring bugs or problems with the device?
Check the internet. They are legion, and won't take you long to get even publication articles now saying the same things as many users. Seems if you get a "plain vanilla" device (mine is an i5/4GB/128GB), you seem to have fewer issues. If you get an i5/8GB/256GB - there are more issues. The i7s seem to have a lot of issues. Battery life is nothing near an Air (I have a 2012 i7/8GB/128GB Air), and almost 4 years later can routinely still get at LEAST 6-7 hours out of it surfing the net/email/etc. The SP4, when I got it would go for maybe 3.5 hours, with display set way down, and doing all the "tricks" everyone recommended to extend battery life. The last firmware update seems to have fixed this for most, and seems to have solved my general issue of power draining even when off. To be honest, Apple isn't without their issues too - but they generally seem to be more "niche" when they do, and not anywhere near as widespread as the SB/SP4 issues have been. So I'm not casting stones here, but it certainly seems the SP4 came out well before it should have (with many pubs and pundits now saying the same thing).
2. How is the keyboard and trackpad?
Not like the Air keyboard, or a Mac keyboard in general. Trackpad is ok, but I've found that when you want to "tap-click", where a Mac will use the entire surface of the trackpad for a click, the SP4 keyboard uses the left side for single click, and I think the right side for right click, but that never seems to work for me. I always use the "two-finger" click on the trackpad for a right-click, and that again, only works on the left side of the trackpad. In general, keyboard is ok (to be honest, I originally thought the "chicklet" keyboard on the Mac would be awful - memories of the PC-Jr era keyboard - but wound up loving the Mac keyboard).
Since this isn't about Win10, I'll give the hardware an 8.5/10 for it's CAPABILITIES - which are not yet fully realized IMHO. Right now, about a 5 or 6 out of 10. I hope that MS will fix the issues, but with the progression of new hardware, I'm not so sure they'll get all of them dealt with before the next round of hardware comes out.
So, why did I buy? I've had an iPad since day 1, and still like the platform and iOS. Two things I don't like about iPad (since day 1) - the lack of a stylus and the lack of using a USB interface for more storage, transport, etc. I kept hoping they'd get the USB thing straightened out - they haven't. They finally got the stylus on the iPad Pro - but when purchasing the entry-level Pro AND the stylus - price is essentially the same as the SP4 (after the usual $100 sales that seem to be present quite a bit). Even with the USB-C on the iPad Pro - still no USB "host" interface - so no ability to use a flash card, etc. Yes, one can purchase an "interface" dongle, but I don't want a dongle on a dongle, ad nauseum. And, those dongles are almost ALWAYS very specific about what you can/can't store on them. Or they are "one-way" - into Videos/iPhoto/etc. apps, not into almost any app, etc.
I bought knowing that the hardware is too tempting to pass up for those attempting to get Linux or even OS 10.10/11 running on it. You can google those if you wish. Fairly good results so far - Linux being ahead of OSX efforts. I think the OSX efforts are hampered by the lack of OSX Skylake drivers right now - and I'm sure that can be overcome as soon as the next release of Apple hardware with Skylake on it.
So - there's an "honest" appraisal. It's ok - it ain't no Mac (but might be turned into one). If all you ever used a Mac for was lightweight stuff - well, then most anything else would work. If you use/used a Mac for heavier video/photo/etc. editing - then the SP4, IMHO, won't cut it.