The best thing about this company are the unique people and the opportunity to gain a lot of experience. The company's specialized teams and national clientele allow for you to gain a lot of experience very quickly in a highly technical area. This is a safe and reasonable environment to work in while you get your CPA or EA.
Cons
There can be a high caseload and many of your colleagues may not be motivated to serve clients as professionals. If you aren't licensed and aren't interested in securing a professional license, your advancement and responsibility will be severely limited.
Michael Rozbruch (Founder of TRS) started in the industry about the same time I did (1998), prior to the saturation of the industry when representatives actually cared about helping tax payers with tax issues. I was told he is no longer with TRS.
Cons
If you are an Enrolled Agent, look elsewhere for employment. Only Attorneys with far less experience get treated with respect. Enrolled Agents are not given private space to do their job effectively (appeals conferences, OIC negotiations, etc). EAs are placed outside in cubicles with file clerks.