I had a similar problem with my 4s and upgrading Spotify.

I have an IPad Air 2, running iOS 7 - and I had auto-updates on.  I should of turned it off.  Previously, spotify was a little slow but still pretty usuable - now it takes maybe 20-30 seconds to boot, can take even longer to be responsive, and sometimes will crash randomly.

I'm kicking myself for allowing the updates to go on seeing how I had similar issues with updating on my iphone 4s.  

And while I'm wondering if its just a temporary issue (could it be fixed in the future?) - I'm worried that further upgrading will just degrade performance more.  And there is no ability to downgrade versions (I blame Apple for this as well...).  

So what are my options?  Are there ways to downgrade? Could spotify release a less feature rich version (ie - spotify lite!) that could work better on older devices?