re: upgrades & SWUs & booking via non-UA sites
Just make sure if you are booking thru another *A carrier (LH, US, etc.) for a code-share flight -- even if the actual flight is on UA metal -- that your alphabet soups of fare-basis codes line up correctly.

Last year I booked UA flights IAD-CDG on the US website. Quite proud of myself for craftily saving $400 compared to UA.com AND booking in "W" class. "W" is upgradeable on UA with a SWU (Although the UG is not confirmable until the day of departure at check-in).

Silly me - I assumed that "W" was "W" on all *A carriers. I'm from Ohio where a "w" is a "w". However, out in the real world, the US "W" is not equivalent to the UA "W". The US "W" is apparently lower than UA's on the UG totem pole. That ugly truth revealed itself at the UA check in desk at CDG, where as we all know, trying to rationalize or argue (politely) with the UA staff is quite impossible. I had to suffer* in E+ for 10 hours for the return flight, although biz was sparsely populated. Lesson of the day: learn your airline alphabets before you buy.

Somewhere on FT or this forum, there is probably a list comparable codes. My advice is to Read it. Use it. Memorize it.

* Really taking all the fun out of my 1 night MR to CDG when the whole point was to use up my last two SWUs. On the outbound the agent apparently forced the system to take it, so I remained clueless until the return flight.