Datasheets (i.e. databound grids) in MS-Access and MS-Excel have:
1. Ability to filter column via click on column header.
2. Ability to see all values in column and check and uncheck those you want to filter by (via click on column header).
3. Subdatasheets where you see a plus sign (+) simlar to what you see in a tree control. When you click on it, it explodes below to show you a related table/fields within the grid. This may be a tall order, but it is one of Access' most useful features because the user does not have to look two places or deal with a dialog or pop-up to see header and related detail records.
4. Ability to bind datasheet to database (for add-edit-delete) ... though this can be done with EO now, it takes custom code and plenty of know-how to do it (but it works flawlessly -- just as fast as a bound datasheet on a local network).
If your grid control could be expanded into a Datasheet control, you would have the first one on the Web and it would sell very well. Please take a look at MS-Access datasheets if you have not already. Business application users everywhere are scrambling to find this kind of functionality. They want to create asp.net database applications with desktop-style UI's but are limited to simple/non-functional grids or ListView controls. Your grid is SO close to what is needed out there already.
Also, on ListView controls there is a group and subtotal function that is needed for your grid to be functionally equivalent, though it is already superior in other ways because a listview, among other things, doesn't have a live edit mode for the whole grid -- you have to edit one row at a time which gives grid controls like yours an enormous advantage.
Subdatasheets