I've run a bunch of classes how with the Kestrel KST 1000 shot timer, and feel I've used it enough to give you a good rundown of the product.
Overall, it's a GREAT timer. I mean it is the BEST shot timer I have owned or used, and I've used just about everything out there. The biggest selling point: Kestrel NAILED IT by making sure the core functions of the timer that we use 95% of the time are EXCELLENT. Other times have added bells and whistles, app connectivity, etc - but they come up short when it comes to the basics.
The basics you need IMHO:
-LOUD buzzer (adjustable is nice and Kestrel has it)
-Quick to switch between instant / delay
-Quick to set par times
-Excellent clip
-Easy to adjust sensitivity
-Waterproof (Finally someone did this! We train outdoors!!!!)
-Easy to read times, splits, etc
and then they did a bunch of extra stuff really well.
There are a few things that could be improved or I'd personally find very useful:
-Minor tweaks to how you scroll through the menus to make things more efficient.
-Adding texture to the "GO" button so I can find it without seeing it
-Stronger backlight
-Adding a random par time function
-Allowing you to re-name custom sensitivity settings
-More pre-sets