Pros
Excellent training. Block is a great place to learn about taxes from the ground up. They will teach you everything you need to know to do a personal income tax return. Also, the pay was good at my office. They paid based on a percentage of the dollar volume of tax returns prepared. In my office the hours were extremely flexible and there were several experienced preparers that could answer any question known to mankind about personal taxes.
Cons
It is my understanding that most offices do not pay as generously as mine did (though that may have just been what the branch owner told me so that I'd think I was really lucky to work at his office). One of the hardest things for me was dealing with a lot of low income people that were struggling financially and then having to offer them rapid refunds - which can be very expensive - just so that they can get their refund a week or two faster. Even though I explained to them that they could wait and not pay the additional fees, I still felt like the Block way (in regards to rapid refunds) was that if the customer didn't know better then that was their problem.