I can't imagine why you've not seen this news, but just in case, with the release of Notes / Domino 8.5.1 next Monday, Domino Designer will now be free.
This is huge news for the platform, as it means that anyone can download and have a play with 8.5.1 which is the first really good version of Domino Designer on Eclipse. It means that you can have a play with XPages without having to worry about CALs. And I'd really recommend taking that look, whereas XPages in 8.5.0 were very much a "dot zero" release, with 8.5.1 we have a vastly improved dev environment and hugely increased performance and stability on the server side.
If you're in any doubt about what you can achieve with XPages in a relatively short amount of time (i.e. less than it took us to develop the first version of IdeaJam), then have a look at http://IQJam.net, the first commercially available application developed specifically for Domino 8.5.1 using XPages.