GABA is the kind of program that's not going to hold your hand. Some people, especially those coming to Japan for the first time, may find that daunting but for a certain type of person it works very well. I liked that GABA didn't tell me what flight to take to Japan, where to live, or when my days off were going to be.
So if you're independent and motivated, this kind of program would suit you.
The pay is based on how many lessons you teach in a month, so you can make quite a bit of money once you're established as an instructor. The flexibility of the schedule also means you can plan time to travel / go on vacation / entertain friends visiting Japan, or work on side projects: a lot of other instructors I know are musicians, artists, freelancers, etc.
I really enjoyed the one-to-one teaching style, which I personally find less stressful than a classroom environment. It gives you more opportunity to strike up a meaningful conversation, get to know your students (or as we call them, "clients"), and meet interesting people.
What would you improve about this program?
Before you start teaching you're required to attend Initial Certification, which is unpaid. The first month at GABA can be difficult, as you don't teach a full month due to the first week of certification. Also, as a new instructor and unknown to the clients you'll have less bookings (students requesting your lessons) and more (unpaid) downtime.
So during this time, it's important to make yourself available for many lessons and make a good impression in order to build your client base.