The easiest way to explain the Sennheiser CX-150's is that they do what you can reasonably expect. You can't really expect much from a pair of sub-50 dollar IEM's, and frankly, I was pleasantly surprised by the general quality of the CX150's.
Pros: Punchy Bass (especially for a pair of low-grade IEM's), Relatively comfortable, handle vocals very well
Cons: Incredibly microphonic cable, cable also very prone to tangling, tips tend to fall off
Summary: I bought these at a closing sale for $20 and they were definitely worth the money. The bass is excellent for bassheads on the go and the sound isolation is excellent for noisy areas like bus rides. They are pretty comfortable and are easy to fit because of the shape.
Pros: bassy, great quality, very solid build
Cons: i had two pairs that broke after a while, gave up on them