E-Savers just came out to the four cities in the subject...it references a page http://www.usairways.com/pro/esavers/intl_esaver_eur22jan.htm
that's not yet up, but the rates are from 259 (PIT/PHL -> CDG) to 389 (SFO -> FCO). (Add international taxes and fees as appropriate.)

With this, a fare I was looking at is now $200 different between the eSaver and the V class upgradable fare. Before, it was just $80, and I didn't have any problem paying that. What's the threshold that people use for the cheapest versus cheapest to upgrade when buying tickets.

My rule is generally that I want the cheapest there is, because I'm going to a place to go for a little while, not just for a mileage run. I don't have any problem sitting in Y on a 330, though like just about everyone else, I'd prefer to sit in C. At $200 additional on a $400 ticket for the potential to upgrade (although it shouldn't be difficult at all right now), that seems like a high additional charge whereas I have a lot of other things I could do with that $200, including booking another ticket to go somewhere else.

I appreciate the input anyone else might have as to their perspectives when shopping for tickets.

When I bought my recent ticket to AMS, the price difference was $50. Well worth it for the upgradable fare.

Had it been $200, or 50% of the cost of the lowest fare, I wouldn't have done it -- at that point it would no be as good a deal and I'd have a more difficult time justifying it. Probably better to try and fly UA in E+ if that is an option...