I train my legs 3 times a week. And on one of those days I'd do sprints at the end of session. But that'll be on the light leg day though -- not on a heavy squat or deadlift day.
On my conditioning day, I'd also include Sprints when I'm done with Prowler push/pull and Sledgehammer work.
The sprints at the end of leg session are a killer. I can't hardly walk after that and I'm always close to puking. I always make sure I sprint on one modafucking badass incline until my legs cannot carry me no more. Uusally about 10 rounds of 20-30 secs. Then good stretch, good food and good sleep I usually have DOMs two days later, when my heavy leg session is due. And that sucks, haha.
On the conditioning day, I sprint outdoors, pick up a nice steep hill and go for it.
As for the results; nice, strong lean legs