I tend to sweep 3 or 4 arps in a row diatonically (or at least close to diatonically) as kind of a 'break' to add some colour - either that or at the peak of a solo I'll get faster / higher and end with a sweep & tap etc....

I don't use them alot, but when I do it tends to be gratuitous... I'm not sure I could claim I add them 'for the music'.... I just like to do it.

As a variation on the theme, I tend to rake quite alot as well - not quite the same but I do it for the same sort of reason, just to break it up. I do an instrumental piece while the singer takes a quick break in the set, and I feel that 5 minutes of constant shred isn't too pleasing to the non-guitarist ear. A few percussive clicks also have their place....

When I first learnt to sweep 5 strings I used to just thrown in a minor arp up and down when improvising od whatever key I was playing in - helped me to get my ears around their sound, and to understand how to make it fit. I've now got a couple of really tasteless pieces I'm working on that are totally swept, which are more for practice of all the shapes than anything else - I might use bits of them live, but i already over-play, and it's a bit of a bad habit no matter how much I enjoy it...