If Fusion is not running and I leave my MacBook Pro (running SL 10.6.4) alone for say 10 minutes, it will go into a power save mode which requires a click of the trackpad to resume. However, if Fusion is running, it still goes into power save mode, but only requires a gesture on the trackpad (ie. a swipe of a finger on trackpad) rather than a click.
I'm new to Mac's so I'm not sure if it goes into a deeper power save mode when Fusion is not running (which requires a click rather than swipe to resume), but if so, then Fusion is stopping the Mac from going into this deeper power save mode (and so wasting battery).
Just to let you know that I no longer have this problem.
I noticed that Windows wasn't displaying the battery status and at first thought it might have been a driver problem, as I was sure I had enabled the setting to pass on the power status in the VM settings. However, when I checked, it was disabled. After re-enaling this option, the power status was shown in Win 7 x64, and I also noticed that the MacBook Pro now went into deep sleep mode.
Thinking this setting being disabled was probably responsible for the original problem of not going into deep sleep mode, I checked again and disabled it, but it still went into deep sleep mode.
So, whether the act of enabling the pass on power status setting also corrected something else, which solved the deep sleep problem, or it was just a coincidence, I'm not sure, but either way my MacBook Pro now goes into deep sleep mode with Fusion running.