Pros
I've been with the company over 2 years and I've seen it change from a slightly stuffy company to one that is more agile and making exciting changes (like a complete renovation of corporate headquarters). We're in the sweet spot in terms of scale (4,000+ employees) since you can do cool things like working across departments on international projects and also have the structure and resources to make things easily manageable. TransUnion growth also allows for greater career opportunities - I've made both a lateral job change, and received a promotion. Overall I'm happy with the direction Transunion is heading and would recommended it as an employer to friends.
Cons
Like any company, your experience will vary by manager. Though we have some great managers, there are some that need improvement (who I personally wouldn't want to work for / with). Be careful to flush this out if you're interviewing!