It's well worth the monies. And this is coming from someone who only played halo for the single player (Multiplayer wasn't for me.) Multiplayer is rather fun on Reach.
I do reccomend though, when you go through your first playthrough solo (If you plan to.) don't do it on legendary. I was on Normal, and Elites -Will- 1 shot melee you (With full shields and full health. And remember, Health doesnt regen in reach, you need medpacks.)