I\'m implementing a jquery based file upload plugin http://blueimp.github.com/jQuery-File-Upload/. There is a sample MVC3 app that you can download https://github.com/maxpav
You could set upload size limit in web.config for concrete controller action using location element:
Where Home is a controller name and UploadFiles is an action name. Size limit is 40MB here.
Still, using Http Handler to process file uploads is not a bad solution if you ask me.