Not super impressed. It has the same problem as Google in that street names are displayed much too sparsely, making it hard to orient yourself. Additionally, the satellite view is too dark, at least in my area.

The imagery looks clean but the minimum altitude is much higher than what Google offers, so it's hard to evaluate. (Helpful tip to mapping providers: you don't need more resolution, just let me zoom in on your existing imagery! There is no reason whatsoever to stop at 1:1.)

No street-view functionality appears to be present. Not sure if it's supposed to be, but it's certainly a dealbreaker if not.

And then, yes, there's the matter of failing to support commonly-used browsers, even though it works fine in those browsers when appending a bogus subdirectory name as someone else pointed out.

Bottom line, if there's any reason to use this over Google Maps I'm not seeing it.