We have searched for an add-on for a windows forms application for a large customer project.
The focus was on a fast grid with enhanced functionality, special gauge controls (like traffic lights and tachometer) and controls with a good look and feel in common.

We have bought DevExpress WinForms and were not disappointed…
The properties and events are not self-explaining / logical (for us) in every case, but we have found anything we needed (and that’s the most important).
The XtraGrid is really stunning (and alone worth the price):
- Very fast
- Very complete functionality (everything that is needed is built in)
- Usable also fully dynamic (serve from code) without problems (set a datatable or a list as datasource and format it in code)
- All needed events are there
=> We use it on almost every form in the application (query forms but also administration forms)

Also the text editor with masks saves a lot of time for plausibility checks.
The all-in-all look-and-feel  (picture buttons, tab-control, checklistbox, and so on) behavior of the controls is an important success factor for the user acceptance.
=> There is a big difference between the look-and-feel of a standard windows forms application and a DevExpress powered window forms application…

Further, the DevExpress support staff are really stunning.
We have been developing for over 20 years - DevExpress is the best support ever.
In almost every case we had feedback in a few hours and the support don’t give up until a problem is solved.
We only wished we had bought earlier as we could have saved a lot of time with it and reached a better user acceptance with it.