I came from the GS2 to my GS3 over the last month. I'm happy with my move but it also may depend on what you think is important. IMO, The biggest features would be a slightly larger screen, 4G/LTE, zero slow downs (GS2 has 1GB RAM, GS3 has 2GB), and continued support since it's the latest.
I don't know about it being buggy because I rooted both phones and am running Jellybean now. Although the GS2 is also slated to be upgraded to JB as well as GS3. I've had over 100 apps installed on both phones but didn't experience a lot of app freezing or errors. At least not any that would cause me frustration. Although, I would have to reboot my GS2 often because of low memory and becoming sluggish. I don't have that issue on my GS3. I'm a bit miffed at the buttons on my GS3 though. You lose a dedicated Search key and the home key is a physical button. I like using Voice Search but can no longer activate via long press Search. I also don't like having to apply so much pressure to depress the home key compared to an easy and light tap on the GS2. I feel like my phone might slip out of my hands.
Also... if you get the GS3 DO NOT drop it. Buy a case. In a drop test video the GS2 passed extremely well but in the GS3 drop test the screen was severely damaged. Gorilla glass isn't so great with shocks from sudden impacts. If the aforementioned reasons to switch are not that big of a deal to you then stick with the GS2. I'm happy with the switch but I wouldn't say that it was a HUGE difference for me.