You get the joy of knowing you're so close to paying for a B fare, you can taste it, but you don't get the EQM. Of course, there's the added insult that you have to spend 15K more frequent flyer miles on each international leg to upgrade.

I did a quick analysis a few months ago on the cost of a mile for B vs. H on a sample itinerary and it's usually not that much more than the H and the value of the underlying mile isn't obliterated. If you look at it like this, you'll see what I mean (i.e. without complicated math, like long division), on say DEN-LHR, my most common route, in C, upgraded:

Y/B -30K miles RT upgrade + 150% EQM + $1250 inc. taxes + 20K FF miles
H -60K miles RT upgrade + 100% EQM + $850 + 20K FF miles
XY -70K miles RT C saver ticket outright + $85 + 0 miles + 0 EQM

Plus, EQM. I think it totally sucks, personally, but UA will get your money any way you'll get it. Plus, it gets you out of that huge flood of FF miles that you weren't sure how to spend. I'm a firm believer that miles are for international upgrades or domestic tickets that are outrageously priced for short notice travel. You miss out on mega EQM if you don't buy international (as well as mega miles for 1P/1K).

Timothy