Ok guys this has been said many times before but I guess repeating it wont hurt.
Yes Blu-Ray disc are a bit more expensive than other disc but not by much and it still cheaper then the $60 you will spend on a regular disc.
Now with that out of the way.
It WILL NOT I repeat WILL NOT take long to DL
PS3 games at the current time because at this point there isnt a single game that takes up the full storage of these Blu-Ray Disc. At most games are only 10GB to 13GB which will only take you a bit longer than it would take you to DL a 360 game. So with a fair connection at most it would only take you like 10hrs.