I've just released version 0.3. This version makes it possible to set the opacity of the lines to any value you want and stores it over sessions. As I think not too many people will be using this option, I just created a simple bookmarklet for this instead of adding it to the settings menu:

I've also encountered some orange dots. I think those are 360° photos of places. Or maybe they're standalone photos, while the blue ones are somewhat connected like street view.

An alternative solution would be this bookmarklet that toggles the visibility of the layer: As a more permanent solution I could make it so that the layer gets shown in the list of layers in the dropdown menu in the top right, but then I'll need to think about what should happen when the street view window is closed. Do I hide the layer again? Do I keep it open because it was opened manually in the layers box? I'll also need to make sure the layer is visible again when you refresh the window.
But all that isn't that difficult any more. I've done that in other scripts before.

Thanks! I'll look into adding that button (or something similar) in the script. I'll be busy this week though.

I'm afraid that is impossible for me to do. I don't have any data to do such filtering on. All I get are the images containing blue lines without any additional data...

I've adjusted the URL in version 0.4, so normally it should work again as before.
Note that no other changes were made yet.

The same issue appears on Google Maps I see. The service from Google doesn't show a blue line there, even though there is indeed street view imagery available. I don't know why exactly this is happening. I can only say I can't do anything about it, I'm afraid.

Indeed. I only request some information from Google in the shape of images and display those. I have no access to the data that is used to make those images.

Yeah, I've been waiting for the migration of the wiki for adding some of my scripts, but that seems to be taking quite a while. I might reconsider that.

Version 0.5 has just been released.
I've now added the layer to the list of layers in the top right menu as 'Street View' so you can toggle the layer whenever you deem it necessary. I've also provided the shortcut combination Shift+T to toggle this layer.

It took me a while to get the logic of when not to hide the layer after exiting street view right, but I think the current solution will feel natural in usage.

EDIT: followed with 0.5.1 to remove a debugging statement that was still present (which didn't have any adverse effects)