I'm screwing with LÖVE now for several reasons: it's viable on mobile, love.js runs in a browser, I like lua and want to learn more, and it reminds me of pygame which I like.

if you think LÖVE is fun, you might be enthralled by http://www.lexaloffle.com/pico-8.php (someone has ported the pico-8 api to LÖVE, also, but the pico-8 tools are just wonderful.)