A new version of NumericUpDown extended control control has been released, including some improvement suggested by CodeProject users (thanks guys :))

Better access to underlying controls

The function to access underliyng (private) fields is now generic and friend.
This allows you inheritors to use it and access all private fields.

Better mouse management

Mouse Enter/Leave events are now handled more precisely by a single method, which uses Rectangle.Contains to test if the mouse is over the control.
This avoids testing the enter/leave from/to the textbox and raises the external MouseEnter/MouseLeave events more precisely (thanks to M. McCracken).

New feature: UpDownButtons can be hidden when mouse is out of the control

A new property allows the UpDownButtons to be hidden and show them only when the mouse is over the control; this feature is useful when you need to save as mush space as possible.
Please note that this is not only a .Visible = False setting, but it involves TextBox enlargement to fill the whole space.
(Thanks to Berryl Hesh)

You can download the new 1.1 revision here, and read documentation here.