Pros
Good benefits Opportunities for engineers and scientists to work on bleeding edge tech aimed at semiconductor manufacturing. Customer demand pushes the R&D and engineering to very short wavelengths, very fast robotics and positioning, wicked fast image processing, and very precise measurements..
Cons
The bottom line is the first line. SemiCap equipment is very cyclical, and KLAC is well known in Silicon Valley for laying people off whenever there's a downturn. There is a reputation, whose truth varies from division to division, of this leading to people and groups hoarding skills and information to make them irreplaceable and layoff-resistant. To be fair, I've heard this mostly from ex-KLAC employees. The location in Milpitas at the McCarthy Ranch intersection of 237 and 880 can be a commute nightmare More and more manufacturing has been shipped overseas, so there is significant 24/7 drift in requirements for senior people to be up early or late for meetings with Europe, Israael, China, etc.