Is the 30 TC even worth looking at?

I would have to agree with MJ. A lot of gun manufacturers come out with new cartridges in an effort to just offer variety, but the cartridges don't really do anything more than already-existing rounds. Winchester tried that over 20 years ago with the .307 and .356 Winchester cartridges. I suspect that Marlin's .308 and .338 Express rounds may meet the same fate, but only time will tell.