As cool as this is, I don't really see any benefits besides having mouse and keyboard support and if the controls are really easy to use, or streamlined; than I'd see maps being able to be made alittle faster. But there's going to be a big learning curve again, as a lot of people already have difficulties with Forging on the X1. The other benefit is being able to Forge on the go if you have a Win10 enabled laptop. I can now finally work on maps when I'm out on business trips!
As of right now, Forge on PC only seems like an extra peripheral. 4k resolution doesn't add anything as the X1 doesn't support it, or if you don't own a 4k TV or monitor than its pointless. So that feature is just a little preference. If the bulk of Halo 5 doesn't come to PC than I personally would choose Forging on X1 over it because there will be important features missing such as Customs. (Although they seemed to hint at Customs as well.) But most of my friends will be on X1 as they don't have decent PCs or don't want Win10. So finding Customs would only be beneficial on X1 anyways unless there's cross play enabled. This is important to test maps to the fullest. Plus I'd still rather be in the comfort of my couch or bed with my headset talking with my friends in a party.
Modding will be next to impossible since it's running off of the Win10 infrastructure and the fact that the game runs off of a dedicated server. So I feel like this whole idea both a good and bad thing. It only really seems to serve as a way to get Halo on the PC scene and open up a way for others to play or get into the Forge mode. As it stands, personally as a Forger, I'd choose building on the X1 over PC. But if I'm away from my Xbox, this serves as a way for me to work while away from home. Probably the only time I'll use it. But I could be wrong?
I could see this as being beneficial if they started a Forgers program that helps Forgers get a little bit of extra cash by working from home to make maps for the game. And if not cash, than maybe it'll allow people who are interested in the program to better have a chance of getting their maps published into matchmaking or something. Sort of a way to get recognition, without having to rely on YouTube or Forge sites. But there's a lot of better alternatives on PC for building maps or even games. As an artist and animator myself, I already have a bunch of studio apps like Unreal, CryEngine, Maya, Ect. so Forge might not get used too much.
But hey? It's nice to have options, so I hope the Forge PC community does grow! This is quite exciting!