The upgrade was mostly smooth for me. I've had a couple of minor issues since.
The lockscreen weather widget doesn't seem to update itself regularly anymore. Noticed immediately after the upgrade. I have no idea what criteria it uses to refresh itself. I didn't change the settings. It's not a matter of not having a data connection. I'm five feet from the wifi and I get plenty of push notifications from other aps all day while the weather widget seems to just sit there. It's not a cache thing; I've cleared it. It only seems to refresh twice a day. I wake up, it says it's something like 55 degrees outside. I look at it again five hours later, it says the same thing. I even tried going into the actual weather app its connected to, but the widget doesn't necessarily refresh. By 8pm, it'll say it's 87 outside, which it probably was at some point in the afternoon. I haven't been able to figure out the pattern of when/why it does/doesn't update.
The second thing is I've also observed worse battery performance, as some others have noticed. It's not terrible, but it's about half what it used to be and the effect was immediate. I'm not sure what it stems from.