It all depends on what you are going to do. With the ones from Bachmann (if they are the ones I think they are) they are just glorified bridge piers. Your track will just be hanging out in the air.
If you are considering embankments and such you may want to look at the risers from Woodland Scenics. They come in varying grades from 1% to 4%.
I am going to have to dig out photos of the old layout that used Bachmann EZ-Track on. The reason that layout failed had nothing to do with the EZ_track it had to do with my poor planning.