Pros
Upward mobility, to a point, though your pay won't follow you very well. McKesson had a cap on max allowed raise when promoted, no matter what you were promoted from and to.
You can learn quite a bit here. Often, especially as a T.E. you are exposed to technology that's pretty new. However, McKesson/Practice Partner is antiquated and doesn't keep up with the times very well, so you will have to tell customers to downgrade or not use some technologies.
A lot of the people that work there are good workers that know their stuff. If you get "stuck" on something, it's quite likely that someone on your team can help, and will help without hesitation.
Cons
Long days for the T.E.s Crazy metrics that changed on a monthly basis made it very difficult to know what to do to get a good end of year review (which your raise would of course be based on). Lots of useless meetings. Money is the bottom line - doesn't matter what work/life balance you have, if you're sick etc. - they just want to know how they can squeeze another dollar out of customers, and why you as the employee haven't done that yet.