I think the magic is gone. There never was much to gain from promocode usage, a few dollars at best. Then dreamhost started there own promo's that were beating any deal you could create with a promo code. I think all in all I had two redeemed.
The only codes that have amazing value for the customer are the codes that include Free IPs for the life of the account. If someone knows in advance they will need multiple dedicated IPs, those codes still win, but for the most part the dreamhost promo's always beat out the customer provided promo's.
I added codes in my signature during the time dreamhost was paying bonus dollars, but even then the dreamhost promo was a better value than any customer generated code (except one with 3 IPs that is).
There is also only a very small handful of forum regulars these days.