If you, like me, are spoiled by the joy of XT/XTR shifters and you find yourself having to use a new, perfectly usable 9-speed drivetrain with an Acera/Alivio shifter, there may be a not-too-costly way out. A quick look online shows that all sub-10-speed Shimano shifters use 1.7 pull ratio. This means one should be able to use high end shifters from the 9-speed era with current 9-speed drivetrains. You could buy an SL-M770 (9-speed) or an SL-M970 off Ebay or anywhere else you could find one and have the nice feel of a high-end shifter without replacing your perfectly serviceable, new 9-speed drivetrain.
I ordered a SL-M770. Will let you know how it goes.
PS: There seems to be a 9-speed CUES shifter that although not as nice as an M770/M970, can do 2-way release, but ~~I can't confirm whether it uses the same pull ratio yet~~ it's not compatible with the 9-speed Alivio (Hyperglide) mech.
Cues is 1:1, so is incompatible unfortunately. You could use it with SRAM though!
Seems like the internet and some Shimano docs agree.