I've leased my last 3 LS's and like any loan, everything is negotiable. Down payment, number of months, total mileage allowed, end of lease costs and so on. For me it's always been a win-win. You just have to go in knowing how the game is played.
Oh and by the way.... I always mod my LS and turn it back in with no problems. Check out out my photo gallery. I keep all the stock parts and just change everything back before the lease is up. As long as everything is just bolt-on, what's the big deal and my dealer doesn't mind. They do custom work themselves on many of the cars and trucks on their lot. Most times they are sorry that I didn't keep the mods on the LS.
The springs, wheels, tail lights and exhaust were on my '03 and now they are on my '06. When this lease is up, if I don't keep the LS, I'll have a fire sale and get some cash back.
Like I said... win-win.