Underpowered is subjective. It has enough power to exceed speed limits anywhere in North America. Acceleration should be similar to what you have now, better at high altitude. You can expect maybe twice the MPG. At 5000 miles a year, you might save $1000 on fuel costs, at current prices. More fuel cost savings with more miles.
Countered by higher initial costs, M-B maintenance costs, not prepaid as they are with M-B cars in the U.S. You figure out the value of that to you.
Most shops that bought on Sprinter to try, for HVAC, plumbing, electrical service work, or urban delivery, buy more of them to replace their Chevys and Fords.