Ahhhhh yes..... sweeeeeeet.......
Once you go SF unlock you don't go back...
And I agree, paying 30 for the expack owns you the right to use you guns in vanilla BF2.
Besides that.... reaching an unlock rank gives you 2 unlocks insted of one... 1 for BF2 and 1 for SF and the fun part is, that you can spend yout SF unlock on a BF2 weapon, so you are unlocking at double speed.... l this is well worth the money I think...
So buy it, don't wait for X-mas, because when you do not get it then, your X-mas will be down the drain and you spent a moth waiting for nothing and you will still be graitfull for the nice pair of socks you got instead, because those nights playing SF can get mighty cold. One month of not playing SF will be very bad You know what that spells.... DISSAPOINTMENT.
So ask daddy for 30 $ or make someone holler ;-)