I've been using it since the first of February and no, there is no choppiness in its performance. It might take a fraction of a second to open some stuff like the storage settings, but it isn't a deal breaker!
I've tried some games on it. I think the one with the most intensive graphics that i tried was Robotek. No lag at all (Unlike my previous Galaxy W).
Internet access is beautiful. It's as simple as that.
I'll add some more points here:
* No random reboots till now.
* The device rarely gets unresponsive. It still happens though.
* I'm way more satisfied with windows phone (compared to android). I miss nothing from android, too.
* When flight mode is on, the device takes more time to respond for a power button click.
* The 'other' category in the storage isn't that scary, at least for me. Well, it does grow up and is now at 1.3 GB; I still have 3.5 GB of free memory, I'm pretty sure that when it eats up alot of the remaining memory, i'll already have all my needed apps and games etc downloaded already. Btw, I manually downloaded most of the apps that I have on the Lumia 620.