Are you asking this as a general question, or only to compare the ease of use of a laptop on a gig versus in a home studio environment? It's really the same thing except for the additional considerations involved with safely transporting and setting up a laptop on a stage. In general the answer to your question is yes, it's pretty easy if you're computer-literate, but not as easy as putting a hardware keyboard on a stand and turning the power on. A few of us on this forum use laptops exclusively. I started using a laptop on stage almost 20 years ago, with a Titanium PowerBook G4, and went exclusively laptop about 13 years ago.
Do you want or need the additional variety (and increased quality) of sounds that 3rd-party VI plugins can give you? Do you want or need the additional control over a virtual instrument's parameters when you're playing a gig? Are you ready to deal with possible software conflicts and troubleshoot them? If the answer to these questions is "no" then a laptop/controller setup may not be for you. In my case, I started years ago wanting to bring the best-quality sounds to a gig that I could, and I was also an amateur programmer that enjoyed "getting under the hood" of my computers and software.
One thing about going all software is that it won't cost you much to try. You already have the laptop. Mainstage, for $30, has a few decent if not spectacular instrument plugins (I'm not sure if they're the same as what's in Garage Band), controller keyboards in general cost less than workstations, and a Mac's headphone output is perfectly fine to drive an amplifier.
Gotcha.
Looks like I'll do just fine with a controller/laptop.
Best get myself down to the shop to try out some controllers to get a feel for them and what I like/don't like.