I've found it easy to use and does everything I wanted (and more). It has evolved over time and seems to continue to be popular and to have good support.

From the website:

IrfanView is a very fast, small, compact and innovative FREEWARE (for non-commercial use) graphic viewer for Windows 9x, ME, NT, 2000, XP, 2003 , 2008, Vista, Windows 7.

It is trying to be simple for beginners and powerful for professionals.

IrfanView is trying to create new and/or interesting features in its own way, unlike some other graphic viewers, whose whole "creativity" is based on feature cloning, stealing of ideas and whole dialogs from ACDSee and/or IrfanView! (for example: XnView has been stealing/cloning features and whole dialogs from IrfanView, for 10+ years).

IrfanView was the first Windows graphic viewer WORLDWIDE with Multiple (animated) GIF support. One of the first graphic viewers WORLDWIDE with Multipage TIF support. The first graphic viewer WORLDWIDE with Multiple ICO support.

Some IrfanView features: Many supported file formats (click here the list of formats) Multi language support Thumbnail/preview option Paint option - to draw lines, circles, arrows, straighten image etc. Toolbar skins option Slideshow (save slideshow as EXE/SCR or burn it to CD) Show EXIF/IPTC/Comment text in Slideshow/Fullscreen etc. Support for Adobe Photoshop Filters Fast directory view (moving through directory) Batch conversion (with image processing) Multipage TIF editing File search Email option Multimedia player Print option Support for embedded color profiles in JPG/TIF Change color depth Scan (batch scan) support Cut/crop IPTC editing Effects (Sharpen, Blur, Adobe 8BF, Filter Factory, Filters Unlimited, etc.) Capturing Extract icons from EXE/DLL/ICLs Lossless JPG rotation Unicode support Many hotkeys Many command line options Many PlugIns Only one EXE-File, no DLLs, no Shareware messages like "I Agree" or "Evaluation expired" No registry changes without user action/permission! and much much more