Pros
Good to build your network with board members of the clients. benefits are good (pension, company car, etc)
Cons
Gartner is a sales organisation nothing more nothing less, if you love pure sales of what ever and don't have in-depth IT experience Gartner is the place to get a job. If you are into IT don't join into a sales role. Payment is average, variable payment is terrible from a steady income perspective. as sales you are being thought all the tricks to close the sale quickly as a Gartner sales rep you will never become a trusted advisor to your clients (this is exclusively for the analysts and executive partners). You just need to squeeze the client harder and harder for additional business. Gartner is a company you either love or hate, nothing in between. The external perception of Gartner is totally different than how the company works internally.
