i am looking for both performance as well as ease of learning curve. thoughts?
Janus has some awesome stuff, but I haven't tried anyone else in a few years.
Xtra Grid from DevExpress is good, but the learning curve is steep (for master-detail, anyway). We like it better than any other that we have tested. The price isn't obscene like some other packages.
We use FlyGird from 9Rays (http://www.9rays.net/products/FlyGrid.Net/) its ok and works well with lots of data but there are bugs and development seems to have stopped, so unless you get the source your stuck with them.
We also use DevExpress for other WinForms controls (XtraBars, XtraTreeList) which are very good. There's also a lot of community support from DevExpress.
I recently blogged (and uploaded some code) comparing virtual modes in the DataGridView (WinForms) versus Syncfusion's gridControl. Having used Syncfusion extensively, I found its Grid's performance to be truly at a whole new level. Here is a link to the blog
http://www.dotnetarchitecthouston.com/post/Superfast-rendering-of-UI-data-in-WinForms-World.aspx
HTH
Definitely not ComponentOne. Their service is terrible, it is FIPS non compliant, the supposed virtual mode is quite crappy