Good points:
When enabled, it stores whatever is in your RAM at shutdown to a designated space on your hard drive. This means that the next time you boot, whatever windows and applications you had running when you shutdown will open and run at startup.
This is effective for laptops because it saves you time opening up everything again and potentially wasting battery life with the time it takes you to do it.
Bad points:
It takes up x amount of space on your hard disk. I guess with todays standards of 30 gig hard drives, what's 128 or 256 MB anyway??
It's not really all that useful for desktops, unless of course you tend to have tons of things open at the same time, and would like those same appz open the next time you boot.
And windows of course takes longer to set itself up because aside from the the usual stuff it's got to initialize, it now has to open your appz.
That's about it. I've used it before, it's cool, but the amusement dies quickly. Maybe you'll need it more than I did...