In other circumstances, Sheridan would have made an excellent slave driver on a plantation. However, that's not the issue. He was insubordinate (viz. his direct refusal to obey Grant's order to consolidate with Sherman); he was late at Spotsylvania when reconnaissance and screening were not issues at all; he got steamed about criticism and Grant made his careless remark that sent Sheridan off to Yellow Tavern and the accidental killing of JEB Stuart before scuttling to Ben Butler, a la Kilpatrick; he was caught napping in the Valley before managing to turn things around against a seriously depleted foe.
Actually that last shows a better side of him; he was more at home with a combined force of infantry, cavalry and artillery - a role in which he was infinitely more useful at Petersburg than he was/would have been as a cavalry commander (under Grant or under Sherman in the Carolinas).
FWIW (nothing at all) Snooks has this to say of their first meeting:
He stepped away to set his minions to work and I considered how to play this stroke of luck. If he’d heard of me, I couldn’t say the same of him. At this first meeting all I could see of Little Phil was a ferocious bantam in his late thirties, short of leg and long in body and arm. His clothes looked as if he had them laundered while he yet stood in ’em, dispensing impatient orders to the world. With dark hair and a no-nonsense moustache set in a tanned face, he brought to mind a particularly persistent gypsy hawker. Unpublished manuscript