Pros
Learn useful and efficient ways to manage a differentiated technology business. KLA-Tencor has strong and proven marketing practices so that the products are industry leading. Definitely a good school for techies to understand that customers and marketing matter as much if not more than the beauty or coolness of the technology at work. Hard place to work at for the faint of heart, the culture is pretty much "what you have done for me is great, no what can you do next"... One is never done proving himself which is in the end a rather good thing to sustain or develop one's drive to improve.
Cons
Projects tend to change very fast as the company is extremely reactive to market conditions. If the market opportunity is not clearly defined, or changes during development, then the whole project is canned which can sometimes be frustrating for the development and engineering crew. But most employees would agree that it's better if prevents us to go into a dead end or a commoditized market. Another downside is that the company's benefits are rapidly shrinking in this increasingly competitive environment and one would worry about retention. For most employees, the company seems to not care too much about retention, which sometimes lead to expensive loses of talent or even competition from ex-employees starting their own businesses or joining competitors.