A few quick thoughts on the G2.
It is fast, but we all knew this. Almost all modern smartphones are fast. The hardware on top end devices pretty much makes sure that everything flies. The G2 is no exception.
The notification shade is a wee bit cluttered. With Android now natively supporting quick settings via a second page on the notification shade, there is very little reason to clutter up the pulldown with with all of the toggles. About 1/3 of the notification shade is already full of stuff before you even get a notification. From what I understand some of the other carrier versions allow some of these to be disabled to clean things up a bit, I have not had the opportunity to dig into setting to see what the Sprint version allows to be disabled.
Odd annoyance regarding notifications. It seems that even if the screen is off if an application is running in the foreground you will not see the notification if you pull down the notification shade. You will see the notification in the status bar, but if you pull it down to see more details it is gone. All of this is if the screen is still locked. I only noticed this when using Google Hangouts. I am a very active user of Hangouts so this really stuck out to me. My common practice if I receive a Hangouts notification is to pull down to see a quick preview to see if it is something I need to unlock the phone and respond to. With the G2 the notification disappears when you pull it down. Like I mentioned earlier, this only seems to happen if Hangouts is the app running "under" the lockscreen. If another app or the home screen is where I left the phone before I locked it the notifications seem to work just fine.
I really enjoy the knock on feature, it is very convenient and somewhat necessary because of the button placement on the back. As most of you know you can wake the phone by double tapping the screen, this also works to turn of the screen by double tapping an empty space on the homescreen or double tapping the status bar. Note if you use a different launcher (I usually use Nova) you lose the ability to turn off the screen by double tapping on the homescreen. It will still turn it off by double tapping the status bar, so you don't lose the functionality completely.
The camera seems really good in limited testing. I obviously am not in an environment to test many different scenarios, but it seems good in limited testing. LG has their own version of Photospheres called VR Panorama, it works a little differently than the stock Nexus version, but seems to work well enough. I for one am looking forward to taking some photospheres without having to use some crash prone hacked version of the apk that I currently have on my current phone. All phones should support it at this point.
I will follow up with more impressions as I notice things going forward. Keep in mind that I am using a phone that is almost a month away from release, there still could be software issues that will be addressed prior to release.