Pros
We have better relationships with more Fortune 500 companies than I experienced while working at the Big 4. The commission/bonus structure provides unlimited potential. If you work hard and make it through dry spells, eventually you strike oil and can make a ton of money. Unlike the Big 4 where tax is second fiddle to the audit practice, tax is our business. Everyone actually does client service. There aren't multiple layers of overpaid administrative partners. Everyone is paid based on results, and everyone is accountable. Much more proactive than reactive and willing to battle for our clients. You are free to work when, how and where you want, as long as you achieve the results expected of you.
Cons
The commission/bonus structure isn't for the risk-averse. Some of the expense policies are on the frugal side, but at least they are administered fairly.