I went through this big list of vendors providing Outlook style navigation bars.
Out of the list, 3 stand out in terms of quality of their products.
My ultimate goal was to use the control in a webpart, hence I was using the control entirely through code (no utilization of a designer/SmartPart capabilities)
Out of the 3 above, the telerik product is just exceptional in terms of ease of programability. Its a very good product, is of very good quality, and telerik support is very responsive.
The DevExpress product was equally good, but it had one hiccup which I will mention later.
ComponentArt is a good product, but requires a lot more effort in terms of programming it to get the end result you want. The ComponentArt liscensin is also a bit limited in terms of redistribution.
Comming back to DevExpress vs Telerik, for the cost of the Telerik r.a.d. panel, you could get the entire navigation suite from DevExpress, but the hiccup with DevExpress was, in my very limited time to evaluate the control I couldn't find out how to do nested (i.e. like a tree control) items within a panel.
But other than for that DevExpress seems like better value for money purely on the fact that you get more controls for the same price as Telerik.
If nested items is your requirement then go for telerik.
All the controls mentioned above vendors have live demos of their their respective sites.
tags: sharepoint, nav bars, outlook 2003 bar