For $500 (when purchased with the truck) it's a decent deal as it's a 48amp unit. Most J1772 home EVSE's are 32-40amp, so the Rivian EVSE is a higher rated unit.
Keep in mind, to charge at 48 amps, you must build a 60amp circuit.
It's only 25 miles/hour charge rate because the R1T is not as efficient as sedan style EV's. If you charged a Model 3 at 48amps it would be 44 miles/hour charge rate.
If you look at the Tesla Wall Charger link below, it has info for the 30% Fed tax credit (good for any brand EVSE) an a link to find local incentives for EVSE's too:
Charge your electric vehicle at home with the J1772 Gen 2 Wall Connector, a convenient home charging solution for electric vehicle owners. Simply plug in overnight and charge while you sleep. Providing up to 9.6 kW (40 amp) power output for a single vehicle, the J1772 Gen 2 Wall Connector...
shop.tesla.com
I got my last EVSE, a Juicebox 40 Pro for $25 because my local Utility was offering a $500 rebate on any approved wi-fi enabled EVSE. How could you pass up that deal?