I bought a HH HD for our vintage 24ft class C a few years ago. It worked great the first year, less so after that - lots of random problems with not picking up sensors. We only use the RV 2 or 3 times a year - one trip of 2-3 weeks and one or two long weekends.
Replacing sensor batteries didn't seem to help, nor did proximity to the sensors. While the performance degraded, I also noticed that the receiver would operate for shorter and shorter durations without external power.
I eventually concluded that my leaving the receiver in the RV year round (in Calgary) without being connected to power for many months was damaging the receiver's rechargeable battery. Last year I kept the receiver in the house and connected to power, and it worked significantly better but not perfectly for our 3-week road trip. I suspect that the HH units require a battery in top condition in order to work more reliably.
When the HH unit connects to the sensors reliably, it works well and the temperature sensors really saved us a couple of times - my wife tends to over-use the brakes when driving in hilly areas.
We just bought a new Class A and I started doing research on what kind of new TPMS to get for it. So difficult to tell what is indeed the best and by what margin.
I think I'm going to try replacing the receiver and sensor batteries on my HH and running it on my Subaru for a few months. If it performs well, I'll probably stick with the HH and add a booster - partly to make it more reliable but also because we'll likely start pulling a toad. If it still has reliability issues with a new battery, I'll keep looking elsewhere...
