I've had a workaholic colleague and it does have its positive and negative points. The positive point is that they'll help you out if things get sticky, but the negative point is that they sometimes make a mountain out of a mole hill. What can be done simply and easily may be done elaborately and in a complicated manner by them. And yes, the boss is impressed more by them. You have to decide whether to join the bandwagon and please the boss, or to strive for work/life balance, which the workaholic doesn't seem to think of!