I'd say nay, because I never use DSP modes.
However, I have some more I'd like to add. From a company standpoint, it might be better to add them. I doubt you'd lose a customer because you added a few extra features. However, someone may decide that these DSP modes are a necessity and buy something else. (I don't know who would be so silly, but it's more apt to happen than someone refusing to buy because of the DSP modes).
If I was going to add them, I'd put them all under a single sub-menu somewhere deep within the menu system. Set it up so those of us who don't like and don't use them, while browsing the menu system only come across one entry - "DSP Modes" - rather than having to skip past each individual mode. If we want to use DSP modes we can choose to enter that sub menu and select a mode. If not, it's only one extra button press to ignore them. This eliminates hassle for people like me, but keeps the feature in for people who use it. Just make sure you default it to OFF...
[This message has been edited by Ryan Wright (edited June 18, 2001).]