Thank you all for the mounds of advice and information. To address some of the points raised....
- This will only my second time in Tokyo (my first visit will be next week) so I do have some concerns about being able to navigate the city
- By the time I get on these flights I should be well into PremierEx on UA. My outbound flight to FRA is on LH - so I don't know if that will buy me anything with them.
- My adventurous side is telling me enjoy a night in Tokyo and catch up on sleep on the planes.
Another way for me to rationalize this strategy is to tell myself that I just have to get on London time, even while in Tokyo. So if I get into Tokyo at 15:25, it really is what? 6:30a London? I should be rolling out of bed. Ideally, I would sleep on the ride over from SFO.
I've reserved the Holiday Inn by NRT just to give myself an out if I wimp out.