The stages are quick and somewhat fun. Gameplay and music is amazing as expected. However there are some ideas thrown at the end that really leave a sour taste:

Willy's stages are fine until stage 4 boss. Who thought it was a good idea? Omg that took me forever to grind napalm and not miss any shot. That's terrible design.
Last boss? You better have bubble lead otherwise you can't hurt it and it's game over.

Even with these serious considerations, an enjoyable game that really improves upon the original.