Puritan's has better prices on some things, but not others.

For example with the sale going on now, for d-ribose (which is expensive), buy one get 2 free... I saved about $30. (over iherb)

They do raise their prices for "sales", but even then they can be a "deal". I used to get my grapeseed extract from them, but then Costco started carrying a nice softgel type, so I bought that last time.

After you buy from them once, if you give your email, they will send occasional emails, for free shipping + perhaps a $$ discount coupon. The buy one get 2 free is the major sale I use.
I don't think the savings on their other sales is as great. They only do this one once a year in summer typically. (If you save your catalogs from them, you will see they alter prices according to sales-- this bothers me somewhat, but I think you still save alot in the end.)

In the past Puritan's did not have the "newest" supplements, but I see that is changing. They now have methylcobalamin and the d-ribose which I had purchased at iherb previously.

I think their quality is fine. I've used them for years. But just not for everything.