Pros
Altera offers one of the most varied option of careers in the industry. Altera is involved in Hardware R&D on advanced process nodes, Software R&D on high-level synthesis, EDA tools (e.g Quartus), IP design, SoC design, Transceiver design, Driver development and so much more. Altera also has a firm stronghold in the FPGA market (one member of a duopoly), thus there is less pressure on day-to-day survivability of a company, unlike a startup. Altera also has an risk-taking and innovative culture, despite being in a duopoly. Each generation of FPGA brings with it new capabilities that affects customers. Altera invests in R&D and is very willing to bring new ideas to market. Altera is also a very diverse company, with operations in many countries.
Cons
Altera can sometimes be extremely aggressive and set unrealistic goals, which is unexpected for a company in an entrenched market position. Altera is also still learning it's way on methodologies of larger scale designs on advanced process nodes.