Works well for me, have you got the country settings and language correct. English UK does not respond to some American expressions (thank goodness). Its a nice app, the in car section needs some work and it does not like my cars built in Nokia Bluetooth system. Word of warning with the in car mode if you use the 'Hey Vlingo' option and are not connected to external power it will suck your battery dry very quickly
Ok - the problem you are now describing is different to the one I thought you were originally describing. I don't have an answer but, just to be clear, the issue is that the Android Market app isn't offering you the same choice of apps as your friend sees on their phone? You say you are on Orange/T-Mobile... I am on Orange in the UK and I can see the Vlingo app in the market. I take it that you and your friend are both on UK contracts and networks?
If you search in the market for "Vlingo", what results do you get? The first answer for me is "Vlingo Virtual Assistant"... I take it that you don't get this?
If you look at Menu -> Settings, is it set to "Show All Apps"?
It sounds to me like your phone is somehow telling the market you have a different version of android than what you actually have. If your phone is not rooted and running a custom rom then I would guess that it is being caused by an app or a launcher that you have installed. The only way to find out would be to uninstall things one at a time.