Thats better than my connection, i don't see anything wrong with it
There are so many variables that can effect internet speed and connection.
For example, I am paying for a 10mbps connection and yet Im getting over 20mbps on average.
It depends on your location, connection type, and the cable itself. Yes, the cable itself can effect the stability of the connection speed.
I actually had to replace my cable cuz when I first got TWC installed in my house (for the third time) I started to experience alot of speed drops when trying to download anything. After I had someone come over to inspect it, they told me there was alot of noise in my line. Replaced the cable, never had a problem since. Also, the cable used was probably over 10 years old. A bad cable will also result in corrupted/lost data during transfers.
And there is no latency that you "should" be at. It will all depend on what I mentioned above what your latency will be. For example, I can be running 23mbps with a 90ms latency and no packet loss. It also depends on the server you are connecting to. Obviously 10ms will be alot better than 20ms, 20ms is nothing to sneeze at. 20ms is actually pretty good. As long as you are under 100ms, you should have no problem.
And you would know if your speed had slowed down to dial up. As you would be waiting for an hour just for the google page to load up.