I picked up a Trackir 3 cheap off the bay a few months ago. I'd never before tried one so it was a good introduction. I used the basic software having converted an old pair of sunglasses (read removed lenses!). This was a great step forward but found I needed to pay an extra $20 to unlock the full software that gives far more head movement. I also needed 3 reflective patches to utilise the program. I experimented with a homemade clip that slipped onto my headset, and whilst it showed what a massive advantage the upgrade gave I realised I needed something better. I ended up buying the Proclip and to be honest it's been brilliant - even with the old TrackIR 3. I have less head movement than the 5 but the advantages are massive over having nothing at all!
The other posters are dead on - I could never go back to not using one, and it's surprising how many games support it. It feels weird at first, but it soon seems like second nature. I was annoyed about having to pay extra to unlock its full potential, but there you go.
Incidentally I've only just found out about the company's dubious reputation, but that aside I love it. I have no other experience or knowledge of the alternatives.
The other posters are dead on - I could never go back to not using one, and it's surprising how many games support it. It feels weird at first, but it soon seems like second nature. I was annoyed about having to pay extra to unlock its full potential, but there you go.
Incidentally I've only just found out about the company's dubious reputation, but that aside I love it. I have no other experience or knowledge of the alternatives.