The process began after I applied online. I had an initial phone interview with a current TS representative who told me about his work and his view of the company. He lacked much flair in his presentation, but I think I appreciated that.
Then I completed a personality Profile for the company. After about a week, they notified me I had been selected for an on-site interview; I came on Sunday, had dinner with a current employee that night, they put me up in the Hyatt downtown, and the following morning I had a marathon of interviews and assessments.
Two things to take away: (1) the interview process is variable, even within the same department and time period and (2) the company does have some growing pains. Some of my fellow interviewees had already taken their assessments; others, like myself, were tested that day. We were transferred between many different people throughout the day; I must have met at least 10 by the end of it all. About the growing pains, I would say that this is a good sign for prospective employees (this industry is doing much better than, say, the financial industry). But be cautioned that it may be rather easy to slip through the cracks if you don't self-advocate. An example of the disorganization of their growth is that a week after my on-site interview, I received an email from another HR rep asking me if I would be interested in beginning the interview process for TS at Epic. Oops!
A week later I got a call asking me if I would be more interested in the EDI department as an Integration Engineer, to which I said yes (for various reasons, among them, EDI is much smaller than TS as a department.)