It has to be in standby I believe, which is done by holding down the PS button and selecting it.
When it comes to reviews and really anything on a scale where you get a value for how good you did, it's more accurate to have more precise numbers.
Like some sites do a scale out of 4, which means anything in the 75 - 90+ range will score a 3. Thats not really helpful though.
Other sites do it out of 5, which allows for more variety.
Others do it out of 5 with .5 numbers allowed and that is basically just a 10 point scale (even though people insist a 4.5 and a 9 are different).
A 10 scale with .5 numbers allowed is really just x out of 20.
And a 10 point scale with . numbers allowed is really just a 100 point scale.
The great thing about the 100 point scale is that you can give your scores more meaning, since you're not lumping every game into a class of scores. There are also a lot of games that are awesome, but you might not want to give them that bump, like an 8.2 that gets bumped down to 8 because 8.5 is too high. However, after a 100 point scale it becomes pointless.
My editor in chief said it reminded him greatly of Burnout.