I rarely give 5 stars because it's rarely deserved, but these things are worthy. The battery lasts so long that I sometimes don't even feel the need to charge, which has only ever happened with my G903.
The straps themselves are fantastic. Very comfortable despite the battery packs, and they don't hurt after hours of use.
Fantastic, but could be better for 3.0 trackers
As far as practical use goes, I couldn't be happier with the TrackStrap Plus. I do, however, am EXTREMELY worried about the USB-C connector for the 3.0 trackers. The USB connector itself is already bent out of its straight form after charging my trackers once, and I'm afraid of it snapping off.
Great overall, but a few annoying design flaws
I've had regular trackstraps for 2 years now, but as VR sessions grew longer and my FBT regularly died, I decided to spring for the battery straps. They work really well, the extra weight and height has not diminished my enjoyment of VRChat FBT at all, but there are a few annoying things.
1. The USB-C to Micro-USB adapter and micro-USB port just feels clunky and fragile. I think a product refresh with usb-c ports for vive 3.0s is long overdue. Having that stem stick out and risk twisting or bending makes an otherwise solid product, one you'll be moving around a lot in, feel like it needs to be babied.
2. The straps are shorter than the non-pro version. I like to wear shoes while in VR, and had no problems putting the normal straps around the arch of my shoes while playing. But the battery straps are short enough that they don't go all the way around a shoe. This means that I either have to put them under the arch of my foot without shoes (uncomfortable to stand on for long periods), wear shoes but put the straps around my ankles (diminishes tracking quality by not having the tracker show ankle movement), or put the battery strap around the ankle and secure the tracker to the shoes some other way (still allows battery power delivery, but overcomplicates the setup). I wish the straps were ~2 inches longer, so they could easily wrap around a shoe That little bit of length difference you can see in the picture (Left, trackstrap, right trackstrap pro) makes a huge difference in if it makes it all the way around a size 10 shoe..
They work amazingly, worth the cost and very thankful for the product.