It does not work well with a dial-up connection because of the size of the files - it will be verrrry slow. With a faster connection it works well.
Using this mapping utility, you can identify watersheds down to the HUC 12 level (sub-watershed level) and use the identify tool to get area information (in acres and in square meters). It can also be used to locate ag facilities that are permitted for manure management, so if you want to know how many facilities there are in your watershed or sub-watershed you can get that information.
Other items (by no means a complete list) that can be mapped are land use (for 1992 and 2000, so you can see the change in use over time), impaired streams and lakes (1998 and 2002 listings), elevation, slope, soil erodibility, and other things.
I highly recommend using this utility. One note - the DNR notes that the help section is is not complete yet, so there may be some items that you may not be able to get help on right now, but that will improve.