i'd really like to buy the boot enchantments

I like Distortion myself... Boosted effectiveness and lowered cooldowns for Flash, Ghost, and Teleport.

There's also Furor to give you even more than 20 MS while you're in the heat of battle.

There's also Captain which allows the team to more effectively follow up on their initiations.

But really that's why there are options. To each their own.

Captain is great if you're a support champion in the back line (EX: ).

And I always use furor on AA champions that have to follow up. (Ex: , and ).

Captain is great on Janna so your allies (which you are behind) can get away super fast. Just press q to save people from all sorts of trouble.

Distortion can be good on some one-trick ponies. Like if you're an Annie that only does flash + use all abilities, you might want distortion so you can do it more often.

Furor can be useful if you can use auto attacks and kite or chase.

But really, other than alacrity, the rest are only used on certain champions or in certain situations, but that doesn't necessarily mean they're bad.