The Manager's Special rate (WEBONLY or TWEET1 both give you that) is not totally useless, but it depends on the property.

There are two BWs close to SNA. The Santa Ana "Plus" gave me a Manager's Special rate at $2ish under the otherwise-best rate (which was the Internet Special rate), so I bit on that one. OTOH the Costa Mesa (on Newport Blvd) brought up a Manager's Special rate which was about $7 more than the otherwise-best rate (advance purchase), and even several $ more than the AAA rate, so forget it there.

When you use a special code like WEBONLY or TWEET1, it doesn't bring up most rates, just the special rate associated with that code (Manager's Special) and the full rate, or something like that. You have to go back and check again with the special code removed to see the other rates. Given that, I consider it pretty sneaky that they created this code which is sometimes better but sometimes much worse than the otherwise-best rate! I bet a lot of people who find that it saves them money at one hotel will assume it always saves them money, and in that case are probably giving BW more money overall than if they had never tried the code! You can only get savings out of this code if each time you're doing a search you try it both ways...

Btw, just like the Internet Special, I find that at many hotels you can book up to a few hours before your stay. In that case, you're not risking anything by "full payment at time of booking" (which when you book that late, isn't necessarily what really happens anyway).