Bike lock bar jiggles in locked position -- indicative of weakness?
Well, its a pretty low quality lock to begin with, so I'd go for a better lock to begin with (e.g. Kryptonite Evo Mini 5). 

See this thread. I've found that this jiggling happens over the years anyway to a lock (and a lot of locks do it out of the box), but I don't believe it affects the security significantly on a decent lock. Some locks have little rubber O-rings to prevent the rattling when you're moving it (you can buy some at your hardware store and put them on yourself).