I own at DSV1 and 2. Staying at DSV2, You have access (IIRC, M-F) at the JW tennis facility but that's it. But, you can take the free DSV shuttle over to the JW and use their restaurants and go through their shops. You get either a 10 or 15% discount (excluding alcohol) when you use your M activity card. Also, you can do room charges back to DSV1 or 2.
If you stayed at DSV1, you could "use" their Spa. But that just means that you could use their outdoor lap pool, outdoor regular pool, showers, locker, steam room. But if you wanted a massage or facial, you would pay for that. I believe that if anyone reserves a massage or facial, you have access to the spa lap pool and steam room, etc.