I think a lot of what people are seeing when they say that it looks like D:OS is precisely that. It LOOKS like D:OS. The UI specifically. This was the first time we saw it though, and I expect it will look much different by release.
I get the feeling that Swen and the team wanted to make a D&D game, and that WOTC wanted to cash in on the BG name. I'm a fan of all D&D, D:OS, and BG series. I feel bad for the die hard BG fans. But personally... I think BG3 will be iconic in it's own right. Change is always bad until you start enjoying it. If you haven't tried D:OS series, I think it is on sale pretty heavily on Steam right now. Get the vitriol out now. Enjoy the game when it comes out.