There is lots of useful real-world information on UA forums re. upgrading with SWUs and CR-1s. Some flights are almost impossible - there were 40 GS in economy on a recent SFO-LHR flight I was on. Forget about SFO-FRA and SFO-HKG. NRT flights from SFO very difficult. SYD flights are notoriously hard - plus the W fare that you need for SYD flights is almost $1000 - $1200 more expensive than the cheapest fares. So you pay a large entry fee for the SWU lottery - which you may or may not win.