I tested this out by placing n Inbox tree and an Infragistics tree on the same form and the following code:

        private void Form1_Load(object sender, EventArgs e)
        {
            string[ nodes = new string[ {
                "12 - etes",
                "13 - fergfer",
                "19 - grtgrtgrtgrtgrtgrtgrtgrtgrtgrtgrtgrtgt",
                "20 - ffffffffffffffffffffffffffffffffffffffffffff"
            };

            foreach (string node in nodes)
            {
                this.ultraTree1.Nodes.Add(node);
                this.treeView1.Nodes.Add(node);
            }
        }

    In this example, I don't see any problems with the tet alignment. My guess is that your sample is setting some property on the tree that is causing this.

    Perhaps you are using GDI instead of GDI+.

    Maybe it's an appearance like you are setting the font or loading an application style.  

In fact, this is quite the opposite. In my application, I was in default mode (which was equivalent to GDI+, I guess), then I switched to GDI and the alignment became good again. I've already heard of some problems in font rendering with windows (http://www.antigrain.com/research/font_rasterization/index.html#FONT_RASTERIZATION), I do not know if this is related.

I do not know either what am I losing by using GDI instead of GDI+.