The first half is more interesting in the urban sense. The second half is more for getting away from the crowds and communing with nature.

I'm not sure "where" it is, but the part near Gare de Lyon has the wonderful shops underneath it to browse in.

I concur with kerouac. The first part is a bit prettier, I think, while the second part is more isolated, if you like peace and quiet. The second part (the below-street-level part) is a bit like a jungle at times, which can be good or bad, depending on what you're in the mood for. The first (elevated) part is a bit "lighter."

The western end, near the Bastille, is the part with the artsy shops beneath the arches of the viaduct. The parkway is on top, the shops are underneath. A lot of the shops are pretty interesting, with craftspeople making musical instruments and ceramic things and other hand-made things that require a lot of skill (no carved wooden letters of the alphabet or macramé or anything like that).