Yes, I do.
Probly don't need to but, IMO, my beer taste better.
I have extremely hard water due to a lot of temporary/permanent hardness.
I figure, if the wateris good going in, it can't hurt.
In all my previous extract only batches, no matter what I did to the hop schedule, I had a very harsh bitterness. After using 5.2 for top up water adjustment the beer was better for it. I just carried it's use over to all my water (in addition to activated charcoal filtration).