Ventajas
This is a great company to work for - training, development and challenging assignments are provided just as long as your performance keeps up. Most of all my line managers have been excellent - personable and very competent. Even with the unfortunate layoffs that are occurring right now due ot the low oil prices, I feel that Shell has treated employees with respect and have tried to be as transparent as possible.
Desventajas
As with any oil and gas company, when the price of oil dips, employees are at risk of layoffs (especially those supporting projects) and Shell is no exception. Sometimes there can be a lack of clarity around roles and responsibiltiies depending on which team you're on. Also, there are layers of management you have to go through to get decisions made, but I think Shell is trying to reduce this complexity and get more adept at making more fit for purpose and risk-based decisions.