Pros
Great variety of work, lots of good projects and initiatives to get involved with, some very smart people. You can create your own job where you find something valuable that needs doing. Technology is getting more investment than it used to and Barclays IT wants to function more like a Technology company, this is starting to come to fruition. Lots of opportunity to progress.
Cons
Everyone is very uncertain about the future, management seem to have no long term plan (that they have shared at least) so often good talent leaves for something more secure. No top-down leadership in IT, very tribal and bottom-up organization, often leading to overlap on work, lots of duplication and no clear picture of where you fit. Broken processes that have been lost in multiple, incomplete restructures make getting most things done a real challenge. If you work outside of the UK, be prepared to adjust to their time zone, and any other region you need to speak with as part of your role.