The biggest disadvantage is the missing support for multiple languages.
Yes, you can install multiple languages but you can't write seperate content for each installed language...
It's not hard to write such a module yourself but the other problem is the URLs.
You can use the 'Human Friendly' option but yet again, this does not support multiple languages.
For instance /Products/tabid/57/language/en-US/Default.aspx becomes products.aspx but there isn't a possibility to include the language like this /en-US/products.aspx
I know there are 3th party tools like UrlMaster which covers this up but still I think this should be available in such a framework.
The biggest advantage is the ease of developing your own modules! If a functionality isn't available, you can write your own module without any problems!