Pros
Decent pay, acceptable benefits, fair job security. Most of the people you will work with are reasonably pleasant. If you are in the right branch of management (typically Site Facilities), you're going to have a great time and they will offer you a lot of on-the-job training. Despite the long list of cons below, even if you're not on Site Facilities, there are many worse places to work.
Cons
Not all branches of the company are as well-managed as the Site Facilities ones. There is very little information interchange between tiers of management and technicians/engineers. Information does not flow well laterally between teams either, and management seems disinterested in facilitating or encouraging better teamwork. It can often feel like an "every man for himself" scenario between different teams, as blame for problems and responsibility for resolution gets shoved around in a game of "not our fault" hot-potato. Most teams are working on a skeleton crew, and management has had a hiring freeze for over a year now. Because of this, ticket turnover time is stretching into unreasonable periods, and quality of work has overall become much lower than what it once was. The upper management environment seems from below to be very political and cloak-and-dagger. Changes are often made without consulting lower-level employees to see how the change will impact their ability to help the customer, or even whether those changes will be possible or achieve the desired result. Often the first thing a team hears about a major change to their MO is on an all-employee call. Inter-team processes are often half-done, leaving one team with expectations that the other team was never told they would need to fill. Many lower-level technicians operate on a modified DuPont schedule, working 12-hour days for two- and three-day shifts that rotate every other week. This can be advantageous for some lifestyles and allows for at least two weekdays off every week, but losing every other weekend can be very disruptive to individuals with regular commitments, and the 12-hour shift has a habit of exacerbating seasonal depression in the winter months. Finally, rather than hiring from within and enabling upward mobility, the new TierPoint management seems to have a strong preference for bringing in new individuals who don't necessarily know anything about working in a data center environment, much less about the company's particular infrastructure. Many technicians have complained of being turned down recently for engineering roles they were eyeing when hired as technicians, and were initially told were within their reach.