As soon as I got into circuits months ago the winds always seemed to pick up, so I got a fairly decent amount of crosswind practice before my first solo.
My first 3 solos sessions were all pretty much in perfect conditions and it 'twas not until my 4th go at soloing that I actually got to have some fun with a crosswind, 14 knots of it mind you. Didn't feel like it though, but thanks to all those previous hours of dual crosswind circuits I knew exactly how to handle it.
So in my opinion I say it's beneficial before a first solo, just incase a breeze comes along just as they've taken off...