I sold my white S2 to buy a white Vivid. This is my first HTC device as well.
- No Perma-Root (I use many apps that require root)
- Exynos > Snapdragon S3 (S2 felt faster in loading apps/transitions, but the Vivid still feels smooth and quick, especially the browser)
- Speakers are quite low on the Vivid while the S2's were quite loud and clear.
- My Vivid has 1 dust particle underneath the screen. Not a big deal because you can't see it while the screen is on, but its still there.
- SAMOLED+ produces better looking colors, but the higher res screen on the Vivid is a decent trade-off.
Apart from those, I don't miss anything from the S2 and prefer everything else on the Vivid. Vivid has better software which gives a better stock experience. Once custom roms come out, the Vivid will be even better but I'm more than contempt with the phone as it is right now.