i've actually (probably the only one here who) used them; i think they are not trying to 'invent' something new, like Play (not saying that is a good/bad thing), but to make development easier with plain java and standards (jsp, jdbc... - that is a good:). small size is important not only for performances, but also you can easily tweak the code if something goes wrong. and there is no xml config, but annotations and class path search (nice!). i liked the balance. I didn't like, at that time, that i still had to code to integrate things together; but i see that's changed now (hopefully).