How do you see them as a costly investment? If you sign up for the I2 program, the steel and holders are basically the same cost as new steel.
I was skeptical at first, but I really like the I2's and found they helped my skating and connection to the ice. I also use the R1 for roller and switch back and forth, and found this helps my transition between the two as well.
I would love to see Marsblade work with Flare steel, as I think this combo would be unbeatable. I'm assuming Marsblade want to keep pushing their own steel, though, which is pretty good quality in its own right.