Initially I was contacted by a recruiter by LinkedIn. After a week I got an e-mail from another recruiter and set for me the first phone interview. She was very kind and professional, the interview lasted approximately 40 min. After a week, she informed the I passed the first stage and set up for me the next interview with a senior recruiter.
The interview was for 1 hour and it was very intense. The questions were way too specific and in my opinion also not very relevant. I was asked about super small details that I experienced 5 years ago. Actually it was the worst interview experience I ever had.
After a week I received a call from the senior recruiter to tell me that I was not accepted. With all the disappointment that I had, I felt so relieved. When he listed for me my weakness points in the interview, he mentioned a superficial things, that I wouldn't expect from a professional as Gartner.
To make it short, long process, exhausting and not really worth it.