"Dell could sue for unfair business practices (extortion?) if MS tried to raise prices or not sell because of Dell's decision to add Linux, or Opera, etc."
Unfortunately that hasn't been the case. The proposed remedy specifically addresses this issue and will try to stop M$ from retaliating in the future..
Ban on Retaliation - Microsoft will be prohibited from retaliating against computer manufacturers or software developers for supporting or developing certain competing software. This provision will ensure that computer manufacturers and software developers are able to take full advantage of the options granted to them under the proposed Final Judgment without fear of reprisal.