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Full user review
"Great free CAD program"
Very feature full CAD package especially considering the XT version is free (the installer installs both the Pro version and XT version, the Pro version is a trial, you can uninstall it). Don't listen to the idiots that don't know a software serial number from an icon, the software installs and works fine (I install on Windows Vista 32 bit and on a Windows 7 64 bit machine).
Has a few bugs, particularly a tendency to change the size of a call out style dimension line. AutoCAD compatibility leaves a bit to be desired. I have 8 AutoCAD files as part of my project and DoubleCAD was able to open, edit and save only about half of them without mangling the contents.
As far as what's available out there for free CAD software this one appears to be the best. Has some quirks (particularly AutoCAD DWG compatibility), but the only better alternative appears to be AutoCAD LT ($$$). If you just want a CAD (DWG) viewer, you are better off with AutoDesk's TrueView free application, but you can't edit with that one.