Pros
As a former Fidessa employee, the original Fidessa employees that are still at ION are incredibly talented, smart and fun to work with day to day.
Cons
Once ION acquired Fidessa, slowly but surely they added on additional processes (which are overnight fire drill emergencies for ION senior management). Senior management will change their mind and update the process again shortly after and never even review it in the first place. They simply want uniformity and data without supporting applications, or human capital. Senior management feels everything can be resolved with a PowerPoint discussing future plans - but never focusing on resolving today’s actual issues. ION slowly chips away at what sanity you have left and then as colleagues leave no one is ever back filled (due to ION senior management never approving candidates, as they micromanage every task). You are forced to stay the course with an incredibly heavy workload and no potential for relief. This cycle repeats itself with every employee until they have a breaking point and resign.