but apparently it isn't just about saving energy. these windows can also result in better comfort.
it seems though that
Low-E is always worth it ( low cost - high benfit )
Triple Plane is potentially worth it ( not just more thermally insulating but also more sound insulating and more physically resistant to debris, burglars etc. )
Argon / Krypton filled windows almost certainly not worth the high price. ( but make for an interesting riddle / paradox )