I just booked my latest RTW ticket as an award ticket with ANA. This forum was obviously invaluable to me during the planning process, so I thought I'd share a few things I learned that were not super obvious, at least to me, in the hope that it's useful info for others.

We actually booked 2 tickets, business class, with a routing of:

SEA-NRT (NH)
KIX-SIN-DPS (SQ/SQ)
SIN-IST-ATH (TK/TK)
ATH-LHR-EWR (A3/UA)

Total cost of 115000 AMC miles (aka AMEX MR points) per ticket, and we paid USD$490 per ticket in taxes and fees. Total distance of 19532 actual miles according to AwardNexus.

My "tips":

• I found I could enter the entire route as a multicity ticket at matrix.itasoftware.com, enter the exact flight numbers I was considering in the "advanced routing" fields, tell it to ignore availability, and get a pretty reasonable idea as to taxes by subtracting the fares from the total reported. My route came out to $441/pp in taxes and fees according to ITA, plus the additional $25/pp fee charged by ANA (I believe for booking over the phone.) After calling in, it came out to $490/pp, so I feel confident this definitely gave me a good ballpark number.
• As reported elsewhere, most of the european carriers (LU, LX, and OS had more attractive routes available for ATH-NYC) have high YQ fuel surcharges, all were around $570/pp. So I went to some lengths to find an available UA flight for the transatlantic leg, and even though we're transiting LHR we're saving around $1k in total vs the alternatives.
• The Star Alliance RTW tool is good for finding potential flight and route ideas, but ignore it for taxes if you're pricing an award ticket. It consistently gave me a $470 "Airline Insurance Surcharge", regardless of which carrier I chose for the transatlantic leg, despite all I read about UA flights not having that issue. My final routing was reported as the most expensive according to the RTW tool, having $948 in taxes and fees, but that is almost double what I actually paid (and what ITA showed!)
• ANA's site does not seem to like to show availability for even slightly longish layovers. Our ATH-LHR-EWR leg didn't show up there (or on AwardNexus, which just searches ANA, obviously...) The individual legs did show up, it just would have been a 6.5 hour layover. So, it's worth checking united.com and searching any promising routes via the individual legs. As it turns out, when I called in to book, the agent placed us on a later flight out of ATH than I'd found, with only 2.5 hours in LHR, so it worked out well!
• The "surface segments" of NRT-KIX and DPS-SIN definitely did not count against total mileage, unlike normal Star Alliance RTW tickets.
• I originally had DPS-SIN included as well, and having two flights to the same hub (SIN) is totally cool / not backtracking, they were willing to do it, though I wound up having to book that flight separately to keep my total overall mileage down.
• Had no problem starting with USA west coast and ending on the east coast. We're actually starting from BOG, but there's next to no availability to get back home if we were to start in BOG, so I resigned myself to starting in the states. As it turns out just BOG-MIA r/t that time of year would be $500/pp. I found BOG-SEA,JFK-BOG for $732/pp, so just marginally more for a big reduction in total mileage. And that difference meant I had just enough points for business class!

Anyway, hope some of my experience is of use to others!