private bool isEnterKey;
protected override bool ProcessDialogKey(Keys keyData)
{
    if (keyData==Keys.Enter)
    {
        return this.ProcessRightKey(keyData);
    }
    return base.ProcessDialogKey(keyData);
}
public new bool ProcessRightKey(Keys keyData)
{
    if (keyData == Keys.Enter)
    {
        //第一种情况：只有一行,且当光标移到最后一列时
        if ((base.CurrentCell.ColumnIndex == (base.ColumnCount - 1)) && (base.RowCount == 1))
        {
            base.CurrentCell = base.Rows[base.RowCount - 1].Cells[0];
            return true;
        }
        //第二种情况：有多行，且当光标移到最后一列时,移到下一行第一个单元
        //if ((base.CurrentCell.ColumnIndex == (base.ColumnCount - 1)) && (base.CurrentCell.RowIndex < (base.RowCount - 1)))
        //{
        //    base.CurrentCell = base.Rows[base.CurrentCell.RowIndex + 1].Cells[0];
        //    return true;
        //}
        if ((base.CurrentCell.ColumnIndex == (VisibleColumnCount - 1)) && (base.CurrentCell.RowIndex < (base.RowCount - 1)))
        {
            base.CurrentCell = base.Rows[base.CurrentCell.RowIndex + 1].Cells[0];
            return true;
        }
        isEnterKey = true;
        //ProcessDataGridViewKey(new KeyEventArgs(Keys.Enter));
    }
    return base.ProcessRightKey(keyData);
}
protected override bool ProcessDataGridViewKey(KeyEventArgs e)
{
    if (e.KeyCode==Keys.Enter)
    {
        isEnterKey = true;
        return this.ProcessRightKey(e.KeyData);
    }
    return base.ProcessDataGridViewKey(e);
}
protected override void OnCellEnter(DataGridViewCellEventArgs e)
{
    if (isEnterKey && (!CurrentCell.Visible || CurrentCell.ReadOnly))
    {
        SendKeys.Send("{Enter}");
    }
    else
    {
        isEnterKey = false;
        base.OnCellEnter(e);
    }
}

------解决方案--------------------
编辑完 回车会触发 CellEndEdit事件，这里处理一下

------解决方案--------------------
按楼主所所想的方法，何时跳转，可以放到CurrentCellDirtyStateChanged事件中。

------解决方案--------------------
      /// <summary>
       /// 实现按下Enter键是移动到下一单元格，不换行
       /// </summary>
       /// <param name="msg"></param>
       /// <param name="keyData"></param>
       /// <returns></returns>
       protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
       {
           if (keyData == Keys.Enter)
           {
               SendKeys.Send("{tab}");
           }
           return base.ProcessCmdKey(ref msg, keyData);
       }

这个是不换行的 ，你可以试着改成换行的。。。