I ve made extensive use of the DevExpress ASPxGridView and many of their other controls.

As mentioned earlier, the DevExpress controls can create a lot of markup, however, they other a ton of functionality and features. They re pretty easy to use. If all you re needing is a really simple grid control, then it s probably overkill. However, if you want to have features like sorting/grouping, drag-drop re-ordering of columns, hiding and adding columns at run-time, AJAX support, etc. then these controls are awesome.

Recent versions (2009.2 and 2009.3) have introduced a number of performance improvements mainly around reducing the volume of traffic and cycle time involved in round-trips to the server. This has made the controls feel even snappier at the end-user side.

One other key benefit of the DevExpress controls is the support. These guys are excellent at getting back to you with meaningful answers to questions in a timely manner. I also enjoy the fact that they have several releases per year which include enhancements and new functionality. You can see their release history by looking at their release history for the ASPxGridView: http://devexpress.com/Products/NET/Controls/ASP/Grid/whatsnew.xml

All in all, I think it s a good value for the money.

By the way, I have no affiliation with DevExpress, I m just a happy customer.

I can t comment on the DevExpress control, but as you were also asking for alternatives:

I was mainly using Telerik RadControls for ASP.NET Ajax in the past. This is a full suite of controls with many controls (have a look at the demos to get an idea). I think these controls are quite powerful, although you ll need to consult the documentation to take advantage of all the features. In addition, I d like to point out that telerik offers great support (in my experience).

i think the tool is good, but if you are just starting the building of the application i would recommend using asp.net mvc instead of asp.net webforms

I used the DevExpress grid controls on a project and they were excellent. Easy to skin and customise with some great features out of the box like filtering, sorting and AJAX support.

We have used the Infragistics WebGrid. They have great knowledge base and help available from their website.

The feature I liked and implemented was the client side edit of data simulating excel functionality. You can edit the cell by simply moving the arrow keys and without using mouse.

Take a sample look at http://samples.infragistics.com/2009.2/WebFeatureBrowser/Default.aspx

I ve used both and my honest opinion is that they are over-engineered (esp. Telerik) and create a lot of muck in the markup. Also, there is always a learning curve involved in successfully adopting any of these offerings. However, if you really do have to have the eye candy, go for it:-)