I love Get To Work, it's one of my favorite packs. I've never gotten bored of the careers and I love aliens. I don't care about the retail so much, but I know a lot of people love it.
One of the great things on GTW careers is that once you've done all the objectives to get the daily work meter to gold you can easily get your Sim's needs up before going home. There are computers to get the fun up, police station and science lab have showers, you can eat at work, you can socialize with your co-workers etc. You don't have "homework", like rabbit hole careers, so you're free to do whatever you want after work.
Science career is a lot of fun. You can invent some awesome things like SimRay, cloning machine, satellite dish, different kind of serums (with different effects) and a wormhole generator. You can also travel to an alien planet Sixam, either through a wormhole generator or an upgraded rocket ship.