There should be two ways to look at the performance of this phone, from the perspective of using the Optimus L5 (the little brother to the L7) and then to a higher-end smartphone, such as the also LG-made Nexus 4.
Coming from the Optimus L5 - the bump in CPU speed from 800MHz to 1GHz is noticeable, it feels smoother on the home screen and tapping in and out of apps. It's not a huge leap, but it is definitely felt throughout the phone.
The screen resolution is by far the biggest change - ramping up from 480x320-pixel display to a much-better 800x480 display. This is the biggest and best change from the L5 to L7, and something worth considering if you were fighting between these two handsets. The screen resolution is definitely the stand out feature between the L5 and L7 - that's for sure.
Phone calls were better on the Optimus L7, I didn't have the same "lag" that I experienced on the lower-end L5, which was a relief. I did notice some lag jumping in and out of phone calls, to SMS, to Facebook, to e-mail, and more - but hey, that is because I'm used to my Nexus 4 now.
Let's take a look at the camera - the Optimus L7 comes with the same 5-megapixel rear-shooter its younger sibling did, but has a very, very slight resolution bump from 2560x1920 to 2592x1944. This won't be noticeable, but it's worth mentioning. Here are some examples of the quality of the camera:
And now for some video samples:
The photos don't come out too bad, and I was actually surprised with the rear-facing 5-megapixel camera and its video capabilities. The front-facing camera is only VGA-capable, but who takes shots using that camera? It's mainly used for video calls and the occasional "selfie".