I have two major issues with Finder since "upgrading" from 10.12.6 to 10.13.
The first one is that thumbnail previews for Microsoft Office files are missing at random (some files have, while others don't have a thumbnail preview; newly created files after the update lack a thumbnail as well). At the same time, in the "File Info" window the preview for Office files is basically an extremely blurry image, making it unusable. The furthermore applies also to iWork files. Curiously, the QuickLook functionality works properly and you can still preview all of these types of files, however, it's kind of hard to navigate around folders and find your files when a major part of your thumbnails have suddenly disappeared. I have tried various troubleshooting methods such as reinstalling MS Office, clearing Finder's preferences and clearing QuickLook's preferences, but to no avail.
The second issue I have is with the "Recents" and is so annoying that I almost want to smash my MacBook with a hammer and get a Windows computer instead. A just modified file does not always automatically and immediately appear at the top of "Recents". It could take minutes or even hours for the newly modified file to appear on top as it should. Meanwhile, when going to the respective folder, you can see that the file has been modified and if sorting is set by "Date Modified" it will be displayed on top. Relaunching Finder doesn't help at all. This has never been an issue with "All my files" in Sierra and earlier editions of the OS. You would think that macOS would be mature enough that its most fundamental application would work fine, but I guess High Sierra is going to be another round of disappointments.