Created attachment 3112 screenshot demonstrating the bug Despite the fixed width settings which also seems to affect the _height_ of the task list items in a vertical task bar somehow, single task list entries will still enlarge to ridiculous size if you have only one or two of them [see attached screenshot]. Since that looks quite ugly I'd either recommend to fix the fixed width to affect the height in vertical task bars properly (if that was intended to work) or add a fixed height setting for vertical task bars. Xfce4 seems to be the only desktop environment that gets the vertical task bar right apart from bloated KDE4, so if you fixed that bug I'd be very delighted to be finally able to use vertical task bars on my small screen also in lightweight DEs properly.
4.8 (you can grab a development release of xfce4-panel if you want to try it) will rotate all the labels 90 degrees, I won't put any more time in 4.6 because time and developer resources are limited in Xfce.
I think for a wide taskbar (200px or something) 90° rotated labels is a very bad idea. You should have a look at what KDE4 does here which is also what 4.6 seems to have done DESPITE the vertical size of each button is somehow broken when there are only few buttons on the list. Wide vertical taskbars are the best thing for a netbook screen with only limited vertical space, and 90° rotated buttons with unreadable text which need more _vertical_ space again (instead of staying horizontal and therefore using the huge width of the task bar up properly) aren't really a solution to this. (Now assuming that 90° turned buttons really means they will lie on the side and I will practically have to turn my head to read the contents properly)
Well if you increase the size of the panel to more then 40px or so, it will add 2 vertical rows of buttons, so space is not an issue. Anyway, I have a netbook too, and you will very quickly get used to the rotated labels, because you only need a glimpse of the label to identify the button, and most often this is the end of a label (filename or terminal location). So yes, they are completely rotated 90 degrees, but no need to turn your head. and the tasklist space if used more efficiently. However I will look into a hidden setting to use the old 'horizontal buttons' in a vertical panel.
Two rows of rotated buttons? Oh dear. Seriously, that sounds horrible. Even old Windows XP can have nice horizontal buttons in a large vertical taskbar! There might be some masochists that like turning their head to be able to properly read weird side-displayed task bar buttons - I am certainly not one of them and I really hope you will include an additional option to have proper horizontal buttons displayed. 90° turned buttons is IMHO practically unusable and even worse than simply having a small horizontal taskbar at the bottom that eats up my precious vertical screen space. I'd rather go back to 4.6 than use 90° rotated task bar buttons I can't read properly! (and live with the weirdness of the vertical enlargement when there are only few buttons on the task bar)
Ok all fixed in ae894f0. There is an option in the dialog to disable button rotation in vertical panels. It button expanding is also fixed with this, they are a normal height.