This page is an attempt to *concisely* pin down the various points for and against the new window control location proposed for Lucid Lynx, to help explain its benefits, and inform the decision whether it is included in 10.04 Final. Hopefully the Design Team (and anyone else) will fill in the gaps when they're ready.
- The left-aligned window controls are in the current pre-release version, decisions will be taken (by the Ubuntu Design Team) during the beta-cycle and before the final release.
- It is intended that the changes will only affect the new themes
- This page is not about how the Design Team have/should have communicated these changes - it's solely about the pros and cons of the design decisions.
Please avoid bloating the page and general bikeshedding
Points in favour
- The Design Team want it (for unspecified reasons).
- "opens up the space on the right" for unspecified "innovative options" to be experimented with in 10.10. 
- Contributes to differentiate Ubuntu from other Operating Systems.
- "Close is more usable on the right" (e.g. by scroll bar, cursor usually rests there) - Needs usability testing data
- Counterargument: "Most people don't scroll with the scrollbar any more"  - Needs stats to verify
- "Button order is confusing" - Needs usability testing data
It will confuse/irritate people used to MS Windows and previous versions of Ubuntu (& other Linux distributions) - seems intuitively true, but needs usability testing to quantify impact.
- It will confuse/irritate people used to Mac OS X - controls on the left aren't in the same order (with close button on far left). No universal toolbar, so controls all bunched together with menu items.
- People seeking the File menu will accidentally hit close - seems plausible, but needs usability testing to quantify impact.
- Close button position will conflict conceptually with other components on the Ubuntu desktop:
- Session/shutdown menu in top-right corner
- Gnome tab close button on the right
- KDE apps?
- Possible conflict/churn in relation to Gnome Shell (e.g. hot corners) - Needs clarification/testing
- Conflicts with SABDFL's plan to "*reduce* customisation, not increase it."
- Close on opposite site of the Min/Max buttons will make it a lot harder to close the window by accident
I expect all these points have been independently discovered and posted on many forums, mailing lists, and blogs - too many to list them all, although they probably all made an appearance on bug #532633.