Pros
Dell has been in constant change for the past 5-7 years, not always experiencing a soft landing after each time they try. However, those periods of turmoil offer the most opportunities for growth, and for the most part, those are available for those who seek them. In the process, and if you try to intentionally navigate those waters with open eyes, you will become wiser and more resilient, and will probably learn more about organizational politics than you would in a more stable corporation.
Cons
Seeing so many things change all the time, it is inevitable you will witness your share of unfairness. Up until the time I was there, Dell was well known by bring in people paying well below the market, all the while demand more than the market would. Some manager tried to fix those injustices by themselves but for the most part it was very hard for them to do anything significant when so many employees were dissatisfied with their low pay.