These have been ported over but they have basically spent the last year working on them.
Only Halo Reach is available at the moment and I played it abit last night and it played extremely well compared to how it played on the console.
If you liked the games on the console but prefer the pc platform then you will like them, but if you didn't like them on the console then playing on the pc is not going to be any different other than it running better and having keyboard and mouse.
The thing with these games is, that only Halo 1 and Halo 2 were ever released on the PC but with this collection there is also Halo 3, Reach and Halo 4, so you get all the FPS Halo games except for Halo 5 for £30 which is not bad.