Hi Robert, I bought an elliptical trainer a few years back when I was suffering badly from compartment syndrome and stress fractures. In my opinion there is little other gym equipment that can use most of the muscles in running and gives the same 'feel' as running does. I've replicated every type of running session on my trainer, from hill sessions to intervals to easy runs to a marathon simulation (3 hours on it was harder than any marathon!)
I agree that a stepper is a good tool as well, but the nature of the machine doesn't give it the same running feel as an elliptical trainer does, and I find if you get the hear rate up to running levels you work the legs so hard that much more than half an hour in one go is really really tough , whereas an elliptical trainer, I find, allows you to get the heart rate up to the 85% + range reasonably easy and is maintainable.
I've had periods in the last few years where I've taken 6 or so weeks off running, switched to the elliptical trainer, and within a week or so of getting back to running have returned to the same pace, so they come highly recommended.
If you can belong to a gym I'd recommend getting in on a spinning session, as if you are a bit of a cyclist and ignore the instructors advice to spin on zero resistance and make it a real time trial like experience, I find this replicates an interval running session very well.
If you are thinking of buying a home trainer, I suggest getting the largest flywheel you can afford and fit, as the performance will be better.
As an aside I am selling my much loved trainer to free up some much needed floor space (And as I have joined a local gym, I don't need it as much as I did). I'm more interested in giving it a good home than making money out of it so if you are interested let me know...