My monitor is a wide-format one and the viewing angle is quite bad when used vertically :-( (Dell S2409W). What's yours? In general, do you know the principle(s) to keep in mind when selecting a monitor for vertical use?
Nowadays most LCDs use cheaper techs like TN panels that only give a good viewing angle when used horizontally. You have to look for monitors with IPS or S-PVA panels. The one you have has a TN panel, which is the worst kind for vertical use, I'm not surprised that you were disappointed.
Be careful and triple-check that the monitor you intend to buy uses the right panel technology, some manufacturers lie about it and others sell different techs for the same model number.
I have two Dell 2209WAB and one HP LP2275w (in different locations, I only use one monitor at a time + laptop). Both models provide excellent angles for vertical use and definitely use the panel technology advertised.