In my case it was. But I’m a computer geek so I like doing that.
But you can get by with just a small amount of tweaking. The main thing is setting your box to use your VoIP’s local access point with login/password. Not any harder than configuring a router.
The fiddly stuff like ring times and such can usually be skipped.
Of course, if you want to go deep there’s all sort of fun things you can do with VoIP in general. I forward our number to a cell phone when we travel, setting up Nomorobo is a snap, etc.