I've always loved the idea of controlling just one player and trying to make my way up the leagues.
I found Euro2008 to be quite an enjoyable game as a result (hell, i even enjoyed Libero Grande years ago) but what PES09 promises to do sounds amazing.
On Euro2008, try as i might, i kept on requesting the ball, Pro wont let me do this
On Euro2008, however bad i played i was never subbed, Pro will sub me
On Euro2008 i was never dropped, Pro will drop me
Oh, and the new FIFA be a pro lasts for four season, thats not a career (unless you're matty piper)- pro is going to let me play for 21 seasons, absolutely class. Add this to the other major advantage (that Pro is Pro and wont play like FIFA!) and you have what should be, in my opinion, a ground breaking mode for the series
So, to answer your question, i love master league mode, always have always will (particularly assuming most of my favourite made up players from the last version are back) but will find it hard to fit it in as i am going to be playing the become a legend mode almost non stop for a few months!