Got my Nexus 4 in a few hours ago but haven't had much time to mess around with it. I gotta say though that I already love it from the little time I have used it. I'm coming from the Galaxy Nexus, so the leap isn't a huge one. Anyways, here are a few things I've noticed......
-Compared to the GNex, the colors most definitely aren't as vibrant. It looks good, but there is a noticeable washed out feel to the colors. Not a dealbreaker to me. Overall though, the clarity on the screen is beast. Definitely on par w/ Apple's Retina, IMO.
-The screen is a joy to type on. I'm not sure if anything is different from the GNex, but I swear it feels like I'm typing on a big iPhone when it comes to accuracy. The GNex gave me FITS with accuracy even though the screen size is virtually the same. There was a point where I even contemplated getting a different phone b/c I had such trouble typing on it. I won't have that problem with the Nexus 4.
-The build quality is lovely. I love the grippy edges on it because if it weren't for those, this thing would be tough to hold on to. The phone is lighter than I thought it would be too. It looks like a heavy phone, but you pick it up and you're surprised at how portable it feels because of the weight.
-The speaker is louder than the GNex, thankfully. The only problem is that the phone lays flat, so unless you prop it up somehow, you're right back to GNex sound quality.
-From a few test photos I took, the camera is clearly better than the GNex, as expected. That's a big plus for me, since taking random pics of my 18-month old is mainly what I use my phone's camera for. Comparing it to the latest iPhone (which seems to be the standard in the handset world), I wouldn't say the N4 is quite on par with it. But it definitely is no slouch and should more than suffice for most people.
-The speed is lovely. Apps seem to open up quicker than the GNex. I'm sure it isn't THAT much faster, but I can see a difference. Haven't had a chance to go through the paces w/ it yet though, so time will tell how the processor fares with a ton of stuff running at once.
All in all, this is a solid purchase. Cosmetically, this phone wows me, but that isn't saying much considering my previous plastic phone. As cool as I thought the GNex was, it really is kind of ugly compared to the N4. But other than looks, nothing else makes me say "damn". That said, I would no doubt tell anyone on the fence to purchase this device....it just feels like the next natural step in the Nexus line's progression. Can't wait until the N5!
If anyone has any questions, feel free.....