I had not updated my N9 because frankly, it was working just fine.

These were the issues prior to the update:

1.) An internet connectivity bug that occurred somewhat frequently - Usually after several days, the internet connect would no longer connect automatically. If connected manually, the device would connect, but would not be able to use the connection at all.
2.) Rough accuracy with copy/paste.
3.) Inability to copy/paste tweets. I mean, really...
4.) With bluetooth headset connected, a static type interference sound could be heard when 3G/Wifi was connecting or down/uploading
5.) Can't sync twitter accounts with contacts. Twitter accounts aren't even given their own contact field.

After the update:

1.) Internet connection doesn't disconnect unless you lose service or enable airplane mode, even with 'Allow Background connections' set to OFF. The symbol remains visible. Although by the looks of the battery consumption, it's not active the entire time.
2.) Copy/Paste accuracy is MUCH improved.
3.) Still can't copy/paste tweets for reply. I mean, really...
4.) Bluetooth issue resolved.
5.) Still no contact space for twitter accounts, but if the person's contact name in your address book is the exact same as their name on twitter (which isn't likely) it will merge the two automatically. You still can't manually add a twitter account to their contact though.
6.) Twitter no longer updates constantly. I'm sure this was done to save battery power in some way, but this is annoying. Now, I can't tell when I'm getting twitter mentions because the app itself doesn't update frequently enough. It would help if there were a setting to customize how often you want it to update, but there isn't even that. The twitter feed on your notification page will update, but it of course doesn't show your mentions, retweets, or DM's.
7.) The UI seems generally slower. I'm not sure exactly how much and exactly what ways, but it doesn't feel as fluid as the first time.
EDIT: 8.) The Drive app does not open anymore. Navigation works fine, but opening drive for voice navigation after plotting a course in Maps simply did not work. After 8 minutes of waiting and almost missing my turns completely, I just followed my path in the Maps app. BIG mess up there. The Maps/Drive apps worked seamlessly together before.

It's disappointing to have a phone with the utmost potential and have it be treated like a stepchild. This could be the best phone ever. No exaggeration. Hopefully somebody will care enough to make this a perfect phone with the next update.