I bought a roll of film but never got round to shooting it. Found it unloaded, unprocessed and ten years out of date just the other week! Key thing is that the film is sensitive to IR but that doesn't turn your camera into a night vision device or thermal imager. If it's 1000 ASA it's still only as fast as visible spectrum 1000 ASA (which I also found an unshot roll of!)
Was issued some for a job once, camera had an ir filter fitted to the flash and we used IR lights to light up what we were looking at. Half the team had NVDs anyway but a useful tool then for recording stuff.
This can now be done using an old DSLR body, all DSLR's have a filter that removes IR light. These guys do it ACS costs about £300 to convert. One of the guys at camera club has had it done and the results look really good.
I had a go at this some years back. ISTR I got hold of some film which seemed expensive but it included the processing cost up front...you had to send it to some dive in central London. I got the best results with a visually opaque filter but the exposure was complete guesswork (the film I had worked on the near-IR part of the spectrum so there was no reliable way of measuring the available light) and meant that you had to bracket a scene over quite a large range. This equated to an effective rate of three shots per roll.
The surrounding vegetation turned out as expected but I remember getting some really weird results with natural and man-made fibres.