Just finished up the RG Hi-Nu Gundam and I have to say this is the best gunpla I've ever made so far. Gonna put some of my thoughts here for anyone interested in this kit.
Highlights: great building experience, looks awesome out of box, and has some very impressive articulation.
Overall, I had a really good time building this kit. I always love seeing the moving parts come together and this one is no exception. The legs in particular have so much cool shit going on in them it's insane. The only part that wasn't so great was building the funnels. Each one has quite a few parts to cut out and there's 6 of them so it gets a bit mundane. They do look really good once they're done though.
Out of box, the Hi-Nu looks amazing. Parts are molded nicely with very few mold lines on the body. A lot of the parts are under-gated where they need to be so you won't see any nub marks on the surface. I just did some panel lining and a matte coat, but you really don't need to put in any extra effort to make it look good. That being said, if you wanted to do a custom build it would be sick on this kit.
So I mentioned how the legs have a lot going on in them... The legs on this kit are, by far, the most articulate limbs I've seen on a gunpla. The knees have 3 points of rotation so you can pretty much fold them in half. Plus, the feet/ankles have another 4 (5?) points of rotation so you can move them all over the place. If you look at the 3rd and 4th pictures in the imgur album you can get a pretty good look at the legs (tbf, I did remove some of the skirting armor to get those kneeling poses). The arms and torso are also very posable in their own right. The torso has a neat gimmick that allows for some deeeep ab crunches.
So if you've been thinking about picking one of these up, do it. This is an incredible gunpla kit.