Trim asparagus, cut stems into 1/4-inch-thick diagonal slices, leaving tips whole.
Heat 1 tbsp oil in a 12-inch heavy nonstick skillet over moderately high heat until hot but not smoking, then saute asparagus, stirring occasionally, until just tender, 5 to 6 minutes. Transfer with a slotted spoon to a plate, reserving skillet off heat.
Pat scallops dry and sprinkle with pepper and 1/2 tsp salt. Add 1 tblsp oil to skillet and heat over mod. high heat until hot but not smoking, then saute half of scallops, turning over once, until browned and just cooked through, 4 to 6 minutes total. Transfer scallops to another plate as cooked.
Wipe out skillet with paper towels, then add remaining tablespoon oil and heat until hot but not smoking. Saute remaining scallops, turning over once, until browned and cooked through, 4 to 6 minutes total, transferring to plate.
Carefully add wine and vinegar to skillet and boil, scraping up brown bits, until liquid is reduced to about 2 tbsp, about 1 minute. Add any scallop juices accumulated on plate and bring to a simmer.
Reduce heat to low and whisk in butter, 1 tbsp at a time, until incorporated.