My experience is primarily with NW/KLM...

Difficulty - even for a top level elite to use my miles without extensive preplanning ... especially if I need 2 or more tickets on the same routing.

Having to buy Business Level fares before I can upgrade internationally - and even then I'm paying
5/9 of the miles for a free ticket to upgrade

Unexplained differences in 'taxes' for booking the same trip on CO or NW

For some reason - Flying CO metal using my NW miles almost always requires rulebusting... what a crock

Inability to book upgrades while I book

Inability to waitlist for upgrades

Inability to waitlist on KLM for different dates

Inability to book on partner airlines like MH or DL online

Inability to check DL international availability on DL's website

the fact that we need to have 3rd party web sites to check availability like WPAA lister and galileo...

endless bugs in NW's online booking system... calling reservations is needed too often

inability to get answers to basic questions via email... this applies to more than just using miles. the answer is always call reservations....

maybe that's more than 10...

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doglover