I just did a little research on this because it sounds like a good deal. The best piece of advice I found is that they are not really gift certificates, more like really good coupons. That is they cannot be spent like cash, and they have restrictions.
The $25 coupon says that you must spend at least $35 and that they will charge you 18% gratuity on the price before discount, that's about $6 (if you only spend $35). Still, it is a good deal (especially at $2 for the coupon). Do a little math, bill is $35 add $6 gratuity and the $2 spent on the coupon, that comes out to $43; now subtract your $25 discount and your total cost is $18 for dinner. Decide, is it worth it to you?
Having eaten at House of Blues just once, I think it would be worth it for a dinner for two. We probably spent $25 total (tax, tip, etc.) But with the coupon we could have gotten either more expensive entrees, or an apetizer, or maybe desert and still spent a few dollars less.
Another important piece of advice I found was to call the restaurant before purchasing the coupon to make sure they take them. Apparently some restaurants have asked to be removed from the list and have not. That is probably not the case with HOB, but I would call.
Thanks for the initial tip and the code. We may look into this too. Oh, one more thing. If you use Paypal, use it for this website. I read some complaints where people said after purchasing from the website they had some strange credit charges. These were not from the website itself, but from "banner ad" companies associated with the website.