I went into the degree having done a lot of programming and found the first year of CS fairly easy. However, I was lucky as Glasgow allows you to switch between degrees almost at will as long as you meet the requirements for it during the first 2 years (1st year courses generally only make up 1/3rd of the credits, and 2nd year courses make up 1/2 of the credits for that year).This meant that I was able to peruse Maths, Physics and CS in my first year, and Electrical Engineering and CS during my second year - it was only in the final 2 years that CS became my only focus.
Essentially, I didn't need to decide which degree I would do until the start of my 3rd year, by which point the course had ramped up to the 4 hours sleep per night level, I was loving every moment of being pushed to the edge, and I was very sure that CS was the right choice for me.
Practically speaking, I came out of the degree having covered a bit of just about everything, and in a position to quickly learn anything that I don't already know. I probably could have become better at programming, but a much less capable thinker if I'd spent the 4 years working.
I don't think that every developers needs a CS degree, however I'd say that if you want to tackle really hard problems, the ones that most people wouldn't even dream of solving, then a CS degree is probably the best tool in your box.