What do people think of the Honda Zoom/Ruckus?  

cranky
I like it.
What is the top speed?

Not built for speed
Woody, it's definitely not for impressing those that would be impressed by power. I believe it's a 49cc.
Top speed for me has been about 38 mph, though i have read on some blogs that the engine can be derestricted to get it into the 42-45 mph range. That however, does negatively affect the mileage and voids the warranty (if that's important to you).
State law here says that anything larger than a 49cc engine requires a motorcycle license as opposed to a regular driver's license.
I live in Chicago, so all of my driving is stop-and-go city traffic. This bike suits me fine.

I was asking
With respect to local speed limits. I don't live in the city, so speed limits can approach 45 mph on my daily commute.

That's the only "problem"...
I see with the Ruckus, for commuting, is the 49cc motor. They used to make a Big Ruckus that was significantly faster but they must not have sold well because they nuked the line. As a cyclist I already know what it means to be an annoyance in traffic and it was the LAST thing I wanted for the morning commute. There is and abundance of info on the web on how to mod these scooters to get a little more OOMPH out of them.