Hi Nigel

,
Two parts to my answer I'm afraid, one easy, one not so
Firstly, I always wear a headset to preserve domestic bliss as the sound of Avons/P&W radials at a level I consider 'comfortable' tends to invoke an adverse reaction from significant other/dogs/windows.
Having tried both methods, I would definitely recommend the Track Clip Pro. Its active LEDS are not as badly affected by errant light sources (reflections from windows, furniture etc) which seemed to make the hat clip less accurate in tracking. FYI, my monitor sits next to a window at 90 degrees to it - the hat clip struggled in strong sunlight, the Pro had no such issues.
As to it's worth - well..... Yes, it can help see those pesky switches which are hidden by yokes etc in the VC. It can make panning around 'easier', but needs practice to work out how much movement from you equates movement in the cockpit. I also found your head movements did not always directly correspond to what appeared on screen - eg, I occasionally found that a tilt of my head equated a swivel in the 'pit, but that may just have been my setup.
Another thing to consider is the the TIR will faithfully follow EVERY movement. So, you turn your head to pick up your coffee/sneeze/refer to checklists/look down at yoke to flip a switch etc etc, your sim head moves. If like me you have a chair with wheels on, any slight movement of that = movement in cockpit. Yes, you can switch TIR off/on and centre it easily enough with hot keys, but again, something to bear in mind, particularly on short finals!
Do I regret my purchase - no. Do I use TIR every time I fly - no. Is it handy in the landing pattern to keep an eye on the airfield - yes. Does it make flipping small switches in the cockpit easier - yes and no. Yes, it makes 'em easier to see/get to, no-if it's really small you really have to concentrate on holding still.
At the end of the day Nigel, if you fancy it, go for it, but as DaveB says, it is not the be all and end all.
Rgds,
Colin