Right now, the shuffle feature provides a very bad user experience when used on large playlists. The shuffle seems to only shuffle through ~160 songs even when your playlist is 800 songs long. I don't know if the number is actually 160 but I will use ~160 to mean the number of songs that are shuffled. Which ~160 songs are chosen seems to depend on which song you started with and the current ordering of the playlist you're on.
This is a problem because it means the shuffle feature is completely ignoring the majority of my 800 song playlist. I've been working really hard on this playlist for the past two years and I want to experience it in a better way than Spotify's current shuffle algorithm.
I work in software engineering, and I believe the shuffle experience could be much improved without adding many more CPU cycles/memory consumption/network traffic to the server or the application. if Spotify puts more thought into it, which I hope they do.