Pros
If you're looking to get into and stay in the association industry, then the experience that you will get at Smithbucklin is invaluable. A lot of people at stand alone associations don't have any idea how to do work that is outside of their department (i.e. if you're in events you don't know how to do board governance, if you're in membership you have no idea about how marketing works, etc.) but at Smithbucklin, you get a full range of how everything works at an association. Especially if you're part of an operations team. It's a very collaborative, team oriented company. The internal classes they offer are also wonderful and cover a lot that you might not learn elsewhere. I once heard someone say that Smithbucklin is the McDonald's of the association world, and that's a great way to describe the company and the experience you'll get. The autonomy you get over projects can be viewed as a pro or a con. You will get to work on important projects and have almost full control over them, however they don't pay you what they should for the level of work you'll be doing.
Cons
Smithbucklin underpays. Most people I know who leave for stand alone organizations are getting paid 15k-20k more a year than they were at SB and doing half of the work. The work life balance is fine at the beginning, but with so much staff turnover, the work piles up and piles up. Once they realize that you're good at your job, they'll give you more responsibility and expect you to do more work for the same salary or with minimal raises. There are also the usual negative office politics, but you'll get that pretty much everywhere you work.