Pros
Tetra Tech is a stable company with a varied and interesting client roster with over 300 offices, providing some geographic mobility, depending on your position. Employees have serious and impressive brain power and technical capabilities and there is a great history/pedigree there. They have made some pretty interesting, substantive and timely moves into Canada, South America, and AUS, and, unlike other posters may have hinted at, such is NOT a book-cooking enterprise (TT is a publicly traded company and is pretty conservative on such fronts and frankly it's irresponsible to make such statements). They have had great success expanding by acquisition (more recently than late 90's early 00's during which they bought some duds) and have acquired some sizable, quality, companies that in turn have greatly complimented and expanded their technical capabilities and international reach. Technical senior management is excellent and extremely qualified, and is more strategic and progressive than prior management teams (without outside benchmarking it's hard to know for sure how great their "vision" is but it's a huge improvement over recent history). Technical / Science stars can move upwards pretty easily if they perform, i.e. more responsibility, promotions, and bonuses are definitely available if they are up to the task. Decent, if not remarkable, basic employee benefits, great health insurance, acceptable 401K contribution, stock options (at certain levels), and a generally hands-off, relaxed mgmt. style if you do your job well. Very client and science oriented, a serious and technically solid company and group of employees. Certainly not bad given current economic and employment conditions.
Cons
Overall "blah" workplace vibe, not great pay and light on vacation time, old-fashioned employee relation sensibilities. They pay just enough so that you will think twice about trying to find a job elsewhere (as most companies probably do). Admin management comes up short in vision, experience, and "modern" management sensibilities, including Admin, HR and IT. Corporate support departments are very thin. Lack of adequate staffing, all for the purpose of saving a few bucks, seems very short-sighted considering what the company could be if they turned it up a notch. Not cutting edge in terms of support systems, especially IT, mostly just doing enough to get by and compete--and again, considering the technical brain power of this company they could blow the competition away if they took the blinders off. Company is improving but still needs to get their act together when it comes to being a "big" company--kind of run w/ a small-minded, small-company mindset, though since new CEO it's changing (a bit, and some of which can't be helped due to the autonomy they give the operating units). Very little, if anything, is done in terms of employee perks outside of standard benefit package, the little extras that show support, creativity, and gratitude (and that reflect a basic understanding of human behavior and reward-based management methods) are missing in action. They, surprisingly, seem clueless on this front and operate very conservatively and "un"-creatively on the employee relations' front. Executive management has the typical "protect their own" mentality with HR merely an employee risk management group charged with keeping the masses away from the gates--there is no push for employees to improve or advance (as they would then deserve, and ask for, more money). Some recent hires just below the C-Suite are unremarkable, at best, very old-boys' club type hires.