TBH I miss the days when you couldn't monitor your GPU usage %. I can't even tell you how many hours of my life I've wasted trying to figure out WHY I wasn't getting 99% at all times on certain games (or sections thereof)
The MSI Afterburner Onscreen Display feature is the best for this purpose though ... but consider yourself forewarned ... you won't always see 99%, but that doesn't necessarily mean anything is 'wrong' ... and definitely doesn't mean you're gonna be able to 'fix it' ... so don't get all stressed about it.
And don't forget that using v-sync (or if the game has a built-in framerate cap) means you won't be getting 99% usage (and it's totally logical why you won't) . And in a lot of online games (BFBC2 I'm looking at you!) you often won't get 99% either