Always test your tools (this includes WinFE). Considering that NIST recently discovered that some Ubuntu based forensic boot discs could make modifications to a booted suspect drive (modifies the $logfile upon booting....), these sort of news breaks are a friendly reminder to test your tools. Additionally, when 'bugs' are found in forensic tools, it may help to review any cases that may be affected by a past use of a tool. Even Guidance Software just released a firmware update to a hardware physical write blocker in which writes to the evidence drive were not protected. How's that for reassurance with hardware write blockers being known as the absolute write protection tool?
You can't rely upon someone else's work, you can't even rely upon the label of a box of something you buy. You just have to spend the time to test it personally.
If you've not tested a tool that you used and later find that there was a problem with it, how long will you worry about one of those times you relied upon it to come back to haunt you in a past case?
Better that you tested it ("I know it works because I tested it") rather than rely on someone else to test it ("But the company/website/brochure said it worked...").