I've been writing a simple (but important for me) Web Application these past few days using Monorail, and I will just say it totally rocks. Getting started with a monorail project, without using any wizard is actually pretty easy; I started by getting the most recent successful build. I was able to get the basic boilerplate code, even supporting localization, in very little time, and I've been very happy with just how simple and intuitive it is overall.
The only problem I had a bit was with documentation, as it seems to be a little older and doesn't quite match now. For example, the wiki entries for the Brail view engine (which I prefer over the nvelocity one) suggest templates and layouts should be named with a *.boo extension, when it should be *.brail.
Oh, and by the way, writing brail templates in Visual Studio sucks :-)... if you open the files using the HTML editor it works, but it is too helpful in reformatting the code, resulting in broken boo snippets.