4 isnt bad if you have a 12mbit connection or something.
but for having 100, the upload ratio is stuff as all forget.
download is for multitasking devices on the net. i mean no one computer needs more then a 20mbit. because no game or website is going to let you use anywhere near your bandwidth total for a single device (or ip)
upload is what is golden for streaming, and gaming, and getting good torrent ratios (thus faster download overall)
im told i get 50:15 but i never really see the 15up in full on a test