You got me curious (I don't use Google Voice, but my dad has for a very long time) and I started to search around. It looks like all the alternatives are either expensive or shitty. :/

Edit: The universally accepted "best" seems to be Grasshopper[1] which is $29/mo or $26/mo billed annually ($312/yr).

[1] https://signup.grasshopper.com/plans