Rated 5 out of 5 stars
1) Transparency problem: this seems to be a bug in FF 4.0 while dealing with DOM drawWindow. I've done hundred tests nothing fix it :(
2) Open in new tab, edit script tabloader.js replace line 14 with gBrowser.addEventListener("TabOpen", onNewTab, false);
3) URL: I've the URL, when the mouse is moving over the thumbnails, it's in the address bar on the right in light gray color.