This is a very personal issue.
Advantages to working:
- It gives you valuable perspective in grad school.
- Sometimes the company will pay for your schooling.
- Gives you time to consider whether you want grad school at all.
- You can save up some money.
Disadvantages of working:
- You get used to the big fat paycheck, and it's hard to take a 75% pay cut.
- You get out of practice of "going to school".
- If you didn't take GRE as a senior, you forget a lot.
- If you did take GRE as a senior, the scores "expire" after a few years.
- Sometimes you lose "currency" if your job doesn't allow you to learn as you work.
So, if you really know you want grad school, go for it. Otherwise, you might consider working for 2-3 years, and then going to grad school.