I found this on the Electronic Arts [UK] Press Site, a Q&A for The Sims 3 Ambitions

The Sims 3 Ambitions Q&A
Attribute to: Grant Rodiek, Associate Producer on The Sims 3 Development Team

QUESTION: Can you tell us a little bit about The Sims 3 Ambitions.
The Sims 3 Ambitions allows players to control their Sims while they are at work in a variety of new careers. Instead of sending your Sims off to work all day, The Sims 3 Ambitions lets you pick a career like firefighting, investigator, architect, ghost hunter, stylist or doctor and then guide your Sim to make choices and succeed (or fail) every step of the way.  You can also make your Sim a tattoo artist, sculptor or inventor.

QUESTION:  Just how popular are careers with the fans? Is this something they have been asking for?
Career gameplay is something we’ve wanted to do for a long time and it’s something that our players consistently request. We always strive to do something new that hasn’t been seen in The Sims before.  We’re especially excited about the fact that the in-depth careers really offer something for all types of players.  Storytellers will love solving mysteries as an investigator or resolving the problems of the afterlife as a ghost hunter. The “gamers” will enjoy being the hero as a firefighter and saving civilians as the doctor. The team cannot wait to see what the Builders and Sim creators make with architect and stylist careers.

There’s a lot of depth and variety here for every type of Sims player.

QUESTION:  Exactly how does the career based gameplay work in Ambitions?
The Sims 3 Ambitions is about your Sim’s personal venture. Each career presents a unique experience.

Firefighters need to develop relationships and maintain their equipment while at the firehouse. But as soon as that alarm rings they need to get to the fire, clear rubble piles, carry out children, stop gas leaks, put out the flames, and be the hero. Your town may fall victim to small fires, huge infernos, and even earthquakes.

Stylists will be hired by neighbors to offer fashion advice and provide partial or complete makeovers.  You can choose to make Sims look really good or just terrible. It’s a lot of power to put in the hands of our more deviant players, but the ability to give the entire town a facelift is fantastic. And profitable!

Using the tattoo chair in game (or at the local Salon) your Sims can tattoo their neighbors with both fantastic and questionable body art, for a price, of course.

The Tattoo System is an incredibly powerful new creative tool for our players. Players can apply multiple tattoos in up to five layers, scale them, change the colors, and even modify opacity. Players can also upload and share these tattoos on the exchange, giving our community yet another creative outlet.

There’s a lot of variety!