Pros:
If you find other canal phones uncomfortable, these have a great design which makes them a joy to wear.
Fantastic price.
Custom sleeves for extra comfort.

Cons:
When listening to music (particularly during quiet songs) any minor scrapes on the cable are vibrated down the cord and you get an annoying noise in your ear.
I have read reviews complaining that the sound quality is bad with the Sennheiser CX3000’s. Compared to top end phones the sound isn’t great but for the price these are fantastic and the sound is pretty good.
For supposedly sound isolating phones these do a poor job. I am guessing this a because of the design which it a two edged sword – the extra comfort takes away from the isolation.

All said, I can defiantly recommend the CX300’s for daily use as long as you have another pair for higher quality home use.