Personally i don't think there is any gain from partitioning a single drive like that, and if you run of room on one partition you are going to be stuck with it.
What I personally do is use two separate drives one for data and one for my os and apps. The reason I do that is I run a lot of alpha and beta software that manages to crash my computer every few months, so this way i reformat my os drive and start over while keeping all my data intact.