This reeks of sarcasm... Honestly though, All I heard was bad things about 4.3 and that led me to not updating at all even with the new firmware out. 4.2.1 works fine for me and I don't use personal hotspot so there is no need for me to update. Every user's needs differ.
Though in all fairness 2.x was pretty good. I stayed on it for a while. Was quite an improvement over 1.x. (Though now on 4.3.3 with my iPhone 4 and I like it as well)
Honestly, it depends on what features you'd actual use if you upgraded. I have an AppleTV, so going from 4.2.1 to 4.3.2 (4.3.3 wasn't out and I haven't upgraded, just installed untrackerd) made sense for me. That, along with personal hotspot (activated through TetherMe) and faster Safari it was a no brainer for me, as they say.