Oh, Proud Mode in KH3D is actually really tough. I'm dying multiple times on boss fights, which I don't typically do in games anymore. Even some of the special link portals have killed me. Just started on Prankster's Paradise, and I'm kind of dreading the claims that other people have made of there being a difficulty spike in the last few worlds. I can't even fathom what Critical must be like...
I personally really like the combat system in this game and BBS - it gives much easier access to flashier, more fun moves without having to sacrifice MP that I might need for healing. That and the flowmotion system makes it really easy to get around, but the huge areas make treasure chests kind of hard to find (which bothers me as a completionist). The one thing that I really don't like about this system is that stat-boosting abilities are linked to the Dream Eaters and can't be permanently acquired. Kind of a disappointment - I'd really like to be able to fill out my ability board... For that matter, I'd like to have temporary party members other than Dream Eaters (particularly in Traverse Town), but system in place works. Dropping started out as an alright feature for me, but it's starting to grate when I'm busy hunting down chests and the like.
Luckily, the story is looking to be really strong so far, and it's starting to bring things together like the series so desperately needed. Can't spoil anything, but Sora and Riku are already developing in the right directions. So far, so good.
TL;DR Proud Mode is actually hard and, aside from a few nit-picks, I'm digging KH3D so far.