Pros
The staff there are supportive, friendly, and genuinely want you to learn. You truly get what you put into it, so make sure you're clear on what you want to learn: SEO, paid search ads, copywriting, web design, etc.
Kontras
As an intern, you don't get paid anything, which was difficult to deal with as somebody with a long commute who needed to pick up a second job to make ends meet. Odds are you won't have a job lined up at the end of the internship, either, but that's typical for smaller marketing agencies.