I use Ubuntu as my exclusive desktop OS.

Ubuntu / Linux has far bigger problems than Unity. (Jump to point 5 for conclusion).

1. There are huge regressions.

With the upgrade to 11.10 my laptop's battery life has been cut from 5-6 hours to 2-2.5 hours. This is on an Asus UL machine that on Windows gets 10 hours.

This may be a kernel issue, but Canonical could add a lot of value by at least warning, or better, fixing/minimizing the problem. There are all kinds of boot parameter hacks, etc. to try to fix this, but it requires a lot of reboots and fiddling with internals. How about including a script to optimize these settings that is run after the upgrade?

"Linux on the desktop" is a dangerous misnomer, because on desktop computers power is not a concern. But nowadays power consumption is almost everything. Canonical already has its sights set on mobile devices, but hasn't even addressed power consumption for notebooks properly.

2. Poor communication of core functionality changes

New additions are presented and lauded in glossy detail, but removed features are not as clearly presented.

Nautilus (file manager) used to allow drag and drop copying/moving of files onto the left pane "bookmarks" folders. This was simply removed without warning, crippling quick drag and drop filing. Once again, this is "upstream", because of the Gnome/Nautilus teams' decisions, but it affects users in a noticeable way.

The initial update to Unity (11.04) removed all gnome applets, and made the time tracking software I used to use inaccessible. The upgrade to 11.10 made me lose my skype app/status indicator.

I don't care if my dock is on the left or bottom, or my open-close buttons are on the left or the right. Most of Unity's "coolness" is Compiz anyway - zoom, desktop switching, etc., so all that was available before Unity. For launching applications, gnome-do is still much faster, light-weight, and flexible (e.g. allowing creating/opening individual tomboy notes).

By communicating feature additions and subtractions better, people won't be so negatively surprised. Set proper expectations.

3. Key consumer software weaknesses

No good media creation suite. I was trying to make a photo slide show with a soundtrack a while ago, and I went through two days of installing/testing, setting up ppa's, compiling sources, etc. to get the latest versions, and nothing really works well. I mostly code, write, and use the web, so it's not mission-critical for me, but for a "consumer desktop OS", the absence of an official and well-functioning suite of applications akin to Apple's music and movie makers is a weakness.

Other apps like Evernote and a more up-to-date Skype would be nice as well.

4. What hardware does it run on flawlessly?

When you buy a computer with Windows or OS X, you know that everything will work. With Ubuntu/Linux, you don't. It's a huge stress factor before buying a new computer. Ubuntu has "certified hardware", but it's buried on some wiki page or other back page. This information should be front and center on the home page, so that I can buy something with confidence that it just works.

5. Conclusion

Ubuntu (whether Unity or Gnome) is far more usable than Windows (messy config menus, no multiple desktops, no full-screen desktop zoom, inconsistent shortcuts, etc.), and at least as good as OS X (which for example doesn't allow you to change the system's font size globally, and is less keyboard navigation friendly).

I'm considering abandoning Ubuntu again, because it can't compete on power consumption.

I am sympathetic to Canonical being annoyed by the bitchy entitlement complaints over superficial UI features (e.g., open/close buttons left or right). It's bike-shedding to the max.

That said, I think better up-front communication of changes can help set expectations. It forces the designers to reason why they are removing/changing/adding something. This doesn't have to lead to drawn out discussions, but some design decisions seem to be "shot from the hip" without realizing that they may affect/ruin ...