I've heard that it's almost impossible to stain as well.

Find a finisher familiar with using dye. Work on samples -- not your floor, to test.

Maple is not impossible to stain. You just need to know what you are doing. If maple is not prepared correctly, it will become blotchy (not burled) when stained. You need to find a finisher (maybe not even the same guy that does the sanding), that knows how to finish maple. Sanding also has a big impact on the outcome. If not prepared correctly, both stain and dye will become blotchy.

Like Al says, you need someone who has experience with maple taking a stain. From my understanding, a dark(er) stain is a better option than a light/mid tone stain. But anything can happen if the technique is poor.

If you are working with an espresso stain, you are probably going to work so dark that the floor will look "painted". Interview several floor finishers. Ask to see a few colour samples that meet your requirements (they should have some made up from other jobs) to show their ability.

If you find someone who looks "scared" when you mention maple, then move on. You will probably have to work with a premium floor professional, with premium skills, premium products and a premium price tag. But someone like that should be worth every penny. Someone with 20 years of experience with a heavy price tag and a guarantee will be worth every cent you pay them. 'Cause if they get it wrong, they will come back and do it again (and again if they have to) at no expense to you.

Going with the "lowest" guy may not get you a nice looking floor. Going high-end should help weed out the "anything for a job" floor finishers. Always ask to see if they have sample boards with dark stained maple. They should have done enough jobs to pull out at least one sample for you.