The only downside to letting W7 take care of everything is that it will create a 100MB partition and stick BOOTMGR on it (and repair utils). If you're familiar with Linux this is basically the equivalent of the /boot partition.
It is generally considered best practice to have a seperate boot partition for the boot loader, that way if you ever install multiple operating systems or your Windows install gets hosed then you will still be able to boot to a recovery environment.
On the other hand you will lose a primary partition from W7 doing this, and some people don't like 100MB being tied up in a visible but "useless" partition, etc.
Different strokes for different folks I guess.
ta
