Well, in getting $50 while depositing $100 for six months, it is in theory a 100% anual return on your money.
However, other factors should also be considered like; going to the bank and spending an hour setting the account up; filling out the appropriate paperwork for your employer to direct deposite (if they provide that option); having to include the $50 it in taxes (if you even bother); haggling with reps over the phone trying to solve problems; closing the account at the end of the 6 month period; and whatever else you have to do to keep the offer valid.
Considering the time involved and viewing it as an hourly wage, you are actually looking at a little over $10 an hour with probably a lot more stress than you would encounter at your workplace. I would think this is a better deal for somebody looking for a new bank.
If you want a savings accounts with good interest as well as some bonus cash, IngDirect provides incentives for creating an account as well as for referring an account. It is purely an online storefront which allows it to provide 2.2% interest and it's easy to access and transfer money. Plus, there are no minimums.
Just some ideas...