I use this shock from time to time (I use the Super Sock-it version - it's just stronger). It works fine, just be sure to predissolve in a bucket.

Consider this however - the bleach will net you about the same cost, and is much easier to use since you don't need to predissolve.

I rarely use the powder anymore - and usually just go with bleach when I need to shock.

These type of cal-hypo shocks almost always cloud the pool a little, but it goes away pretty quick - and if you're trying to clear the pool for a new season, a little cloudiness probably isn't an issue.

The main benefit to the cal-hypo shocks is you can keep a few bags on hand, and they have a pretty good shelf life versus regular bleach.