I think the OP is great. PC gives good advice. I didn't read it at all as if he was saying that no one should by the Nexus, he's just urging caution.
It's an investment, just as Ollie and others have stated. I'm right on the same page there with you other nerds.
However, unless you've used a phone that's pushing that 6" screen size before, you really do need to do your research. Even if you can't get your hands on the Nexus in-store yet, go in and pick up a Note device or any of the others in the phablet range.
Aside from watching countless review and feature videos, this is exactly what I did when I preordered the Note 4. I had considered the 3 when I got the s4 and I went back to VZW to hold/play with the 3 some more after having decided that I thought I could enjoy using a device in this size bracket.
I love my Note 4 now and am very glad that I made the switch, but not everyone has hands as large as mine.
In the end, I guess it's not that big of a deal, though, as long as your carrier has the 14-day (or whatever other carriers do) return policy, because you can get hands-on with the device in your day-to-day routine and really see what works or doesn't for your particular needs...