It's also data from iTunes Match, and leftovers from partially completed music and app downloads. Those botched downloads can take up a lot of space, and unfortunately, there's no easy way to clear them unless you do a factory reset and restore from backup.
1.5 GB is about normal for the "Other" space. On my phone, it will balloon to more than 2.5 GB, but I suspect that's stuff that iTunes Match leaves behind (like when songs fail to load all the way). That, and some misbehaving apps that chew through storage like crazy, is why I routinely do a reset and restore about once every other month.
Another frequently cited culprit is iMessages. If you frequently attach pictures or videos, you will want to delete those outgoing messages because they can take up a lot of space.
