As an update, I also just completed BLR-FRA C=>F upgrade using SWU. The process in BLR was MUCH easier than it was in FRA. In BLR, when I arrived at the airport about 2 hours before my flight, I handed the agent my SWU and she knew exactly what to do. 3 minutes later, I had the F seat. Though I am not sure they were supposed to, I was also given access to the F lounge in BLR, which is just to the right of the Business lounge. I think usually this is only for paid F. It is SO SO SO much nicer being in a good lounge compared to the mess that was the old BLR airport!

In FRA, I had a 5 hour layover and was able to use their terrific FCL in A terminal. For me, the value of being able to use the FCL in FRA was alone worth the SWU. Of course, I could have also used the UA FCL, but the UA FCL is absolutely terrible compared to LH's. The UA FCL in FRA is one of the worst in the entire system.