It’s always worth registering, in this case if only to find out what your offer is. I value Starpoints at 2.3 cents apiece so 7500 points is worth $172.50 to me. That’s not a bad rebate on top of usual points earning and any other quarterly promotion Starwood announces for, say, two 2 night stays (in Lucky’s case).
You want to be registered in any case because it’s easiest to do it when the offer is in front of you, you’ll never remember to go back and register later if it turns out you had more Starwood says coming up than you expected.