Vantaggi
It has been a fairly stable place to work for the last 6 years. The work can be interesting at times. There is some variety, and lateral movement within a division is generally easy. It can be a good place to learn, with a lot of resources (scopes, analyzers, chambers, etc) available, which small companies can't afford. You may come in contact with experts in many fields, research scientists, etc. There are education benefits that might possibly be better than comparable companies.
Svantaggi
I can only comment on xSeries, a subdivision of STG. Depending on the management chain, work/life issues can either be treated well, or badly. Like any large company, creative employees can feel stymied by the bureaucracy. xSeries is/was a large area, with a variety of projects to work on. Many of the hardware projects/jobs are moving to Taiwan, and software to mainland China. The career path of an engineer seems non-existent. There is nothing to work towards, newhires and senior engineers work on the same stuff. Being a capable senior engineer does not guarantee a lead position, or preferential treatment when it comes to layoffs. Dead wood can survive a very long time. It's easier to dispose of a bad employee by sending off with a decent review, so the next dept gets the problem. Employee benefits have been steadily eroded for the past 10-15 years, the culmination being the freezing of the pension plan in '08. The guys with more than 30 yrs as of last year have a nice retirement to look forward to, the rest not so much, and newhires get the worst deal of all.