I think some are worth it, and some are hype. I have always tended to decide which service, software, or provider to use based on how well the particular tool fits my needs (including overall costs). Then, if there's a coupon or discount of some sort, I'll take advantage of that. Sometimes, a coupon or special might help me choose between two similar offerings, but only if the offerings are otherwise identical or very, very close.
Merchants (both on- and off-line) have always used specials and discounts as customer enticement. There will always be good ones and bad ones. The consumer has to make smart decisions. (I think that there are some merchants who count on that, and try and come up with the flashiest/best-sounding text for a special that's otherwise kind of average...but, again, that's advertising for you.)
There are many merchants who use specials and don't try for the Vegas effect (ie, blind people with the glitz). Again...the onus is on the consumer to choose wisely.