The ROMs degree of awesomeness strongly depends on the featured exhibits on display, which is why I'm reserving a strictly 4 star review. Basic entrance fees don't get you access to the special exhibits, but there is still around 3 floors of things to see from dinosaurs, a bat cave, and other regional exhibits with everything from arts and crafts to weapons and heirlooms. It's all what I would describe as mildly interesting at best. These areas are also most rampant with crowds and loud children.
But if you pay for the extra exhibits you can see more exclusive pieces. Right at this moment (until September or so), you'll find 2 amazing exhibits:
-Chiluly (an artist who makes absolutely beautiful blown glass structures, seriously awe inspiring glass works that don't require a lot of thought but still leave an impression)
-Tattoos (a historical look back on the use and evolution of tattooing around the world)
These 2 exhibits were worth the price of admission on their own. Admittedly the more general of exhibits got a bit boring as we continued exploring the space.
BONUS NOTE: When buying tickets online, use the promo code METROPASS to save a few bucks on each ticket.