Some genral thoughts here. First of all, this is a great video by Aris. It shows some of the ways you can utilise JG properly. However, I want to allay some concerns.
JG will not make GI obsolete. They are useful in different circumstances. JG is great against unblockables, and against similar timing mixups like the Hilde 3BA / 3BB as shown in this video. GI has a much bigger window and is better when you see a move coming but don't know exactly what it is, because you know what attacks you'll be able to follow up with.
Because you can bait re-GIs, you can get the double advantgage of getting a much bigger combo than with a JG, and you can waste your opponent's metere. Finally, and this is really important, if your opponent hasn't got enough meter to re-GI, you can use GI for absolutely guaranteed follow up.
With JG, every attack you JG will yield a different advantage: some won;t be launch punihsable, and some won't be punishable at all. JG will be a really powerful tool in the hands of skilled players, but GI will still be important too.
I thought this at the beginning, and I remember Kayane sent this concern to Namco when JG was first announced. Multiple binds do not help at all, because there is a short window after you attempt a JG during which you can't attempt it again. To spam JG, you tap G rythmyically but not quickly, and it's very risky.
