OK, so a few things.
Connection is hit & miss, but when it connects it is useful to change various settings (it's certainly better than the "count the flashes" system Traxxas controllers normally use).
Is it necessary? Not at all, but like Billy I use it with my XO1, and occasionally my ERBE, and it's speed readings are accurate +/- 3km/h, and the voltage/temp alarms are handy to have.
Like anything you have to ask if you'll get the value out of it, but certainly telemetry can be handy if you're trying to track speed or monitor temps and voltage remotely.
from Melbourne, Australia (where Winter is Summer, and we use the metric system)
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