I worked on Landsat and Spot data back in the 80s using American (Gould) and Canadian image processing systems. Both came with Fortran source code, so it was very educational.

ATI tried to recruit me for consumer products, but their understanding of image processing was so primitive that we couldn't communicate. All they understood was red-eye removal and edge detection. :)

The various Landsat resolutions are ok for earth sciences, including ground cover, cloud cover and ice studies.

But I think most of the people here would be more interested in Spot or higher resolution data.

An interesting factoid is that one of the earliest Sony CD-ROMs ever burned (1985'ish) had Landsat sample data on it. It was distributed to a few Japanese geoscientists who had an obvious need for mass storage.