In a nutshell: I wouldn't recommend the average punter buy a Nexus 7 2nd gen due to potential touchscreen issues.
The second generation model was first produced in 2013 -- a lighter, thinner and generally better update of the original Nexus 7. Unfortunately, judging by the number of complaints online, a lot of them have problems with the touchscreen sensitivity, mostly related to taps not being registered when the device is on a surface rather than being held in a hand. It seems to be a combination of grounding issues and the software drivers needing their settings fine-tuning to suit the batch they were produced in... i.e. when Google tried releasing an update to fix most of the reported problems, it fixed things for some people and negatively affected others that hadn't had problems up until that point.
Lots of people seem to have returned them and received back a unit with the same or worse problems, making it a lottery as to whether or not you get a usable device. And whilst there are lots of good reviews out there, they seem to have been written before the 4.4.x software updates that broke things for people.
This all wouldn't be such an issue if Android allowed touchscreen sensitivity settings to be configured by the end user. I know, I know, most people can't be trusted with sharp things...
Fortunately, there are ways around this, but they're too technical and finicky for most people to be bothering with... hence the advice to stay away from this particular model. Nexus releases are great because they come with stock Android and receive updates for a decent period of time, but in this case Asus haven't done a good job of component selection and quality control.
If you have a misbehaving 2nd gen Nexus 7 and are confident buggering around with things, you can try replacing the touchscreen software using the method and resources outlined by a friendly hacker here:
I found the first boot-ts10-lock image improved things massively, although I had a great deal of trouble getting ADB/Fastboot drivers to work in order to load on the modified software. I'm still not entirely sure what got the device recognised -- I also tried official drivers from http://developer.android.com/sdk/win-usb.html and went through a few of the alternative ones supplied by http://www.wugfresh.com/nrt/ -- but the main thing was it seemed to not like some of the USB ports on both the laptop and PC I was using.
Anyway, it did eventually work, and other than the non-standard configuration hassle it's a nice tablet that works well and is nice and light for the size. It's already survived a few tumbles, and fingers crossed will continue to. As a bit of trivia, it has enough processing power to handle DVD streaming wirelessly from a Samsung SE-208BW, which the first Nexus 7 (and from memory the Nexus 10 -- never wrote about experience with that one, did I?) didn't quite manage. It's a shame the 208BW is still an unreliable POS.
What I'm more excited about is the prospect of an 8-9" Nexus device with fairly beefy specs likely to be released later this year, although it's probably too much to hope for that it'll be closer to 4:3 ratio. My ideal tablet is something like an iPad Mini Retina or iPad Air running stock Android, and with the extensive community support and quick updates that come from being produced by a Google partner.
I'd also like official split-screen functionality for apps and a pony that craps rainbows.