+1 for good old Java, rock solid and just works for so many large, mission critical, and high performance (!) systems.
As for vaadin - how far can u get without the pro version? None of the samples include a login, and the LoginView seems to be a PRO feature? It looks full of features.
Vaadin is very nice but I would only recommend it when you can afford to keep the state server side. Vaadin works best when you can use sticky sessions
I haven't checked LoginView, but I guess it will be a couple of text fields, a button with an attached event, maybe CSSLayout, and some javascript code for effects. Something you can easily get done quickly by following tutorials.
PRO components are there you can get something fast with zero coding, but everything else is open source Vaadin.
As for vaadin - how far can u get without the pro version? None of the samples include a login, and the LoginView seems to be a PRO feature? It looks full of features.