Smalltalk is the most lively environment you can have. Pure OO with direct feedback. Not the usual dead code in files with long cycles as in more mainstream technologies

There is a bootstrap package for Seaside, check out the demo page at: http://pharo.pharocloud.com

It is true that meanwhile single page applications have hit the client web space - but you can address them easily with the Seaside-REST package (for instance sending JSON to clients side AngularJS). If you need a framework with less footprint check out "Teapot" which you can easily run on Pharo (http://www.pharo.org).