This is definitely much more preferable to the typical 90 day window + pay the tax this year scenario. Even if the company does not go public, the employee at least now has five years to come up with the money to pay the tax bill. If you are fortunate enough to work at a company that offers a longer exercise period (e.g., Quora and Pinterest are two I can think of offhand that offer 7+ years to exercise your options), then you've got over a decade of time--unless I'm misunderstanding the bill.
Is it possible to "un-exercise" your ISOs? If so, that also gives employees five more years to watch the company trajectory and make a more informed and measured decision -- if they lose confidence in the company, they can return the ISOs to the employer instead of paying an upfront tax bill on what is still somewhat of a lottery ticket.
