Three big issues I have the new Maps app:
1) Traffic data is borderline useless. If there's a traffic issue, you get a red dotted line. That's it. No different colors for different levels of issues. So the road could be shut down because of an accident but it will look the same as if traffic were just slow. It's also very difficult to tell which side of the road the traffic problem is on. Finally, having no traffic data and having no traffic issues are handled the same way by displaying nothing so you really don't know what is going on. Is there no issue or is there no data? The difference between those two could be huge.
2) The default zoom level of street information sucks. At the default level, very few streets have any sort of identification. By the time you get down to a level where all street names are visible, you're down to a couple of blocks on the map.
3) Hybrid view stupidly only seems to overlay whatever is considered a "major" road. So roads that are overhung by trees just vanish into nothingness only to pop up at a hard to distinguish later point.
Not really an issue, but despite all of its wow factor, I still don't see what 3D maps really add to the usefulness of the software.