The Desktop search category is getting lot of attention these especially after Copenic and others released there tools free. I will try to compare the three most popular tools in this category.
The comparison is grouped by most common tasks.
Filetypes:  All these tools can index most common type of Microsoft Office documents, Email and attachments, PDF files, Common Graphic formats and music files. I would give more points to X1 as it can index certain types of Adobe specific documents like .ai and also index Eudora and Netscape emails.
Indexing Options: It is quite similar in all the three tools. You have the option to decide which folders are to be indexed, the folder where index would be stored and also free to choose the frequency when the index would be updated. You can even add new file types but it is limited only text format files. Wish I could index my collection of .chm files !! While indexing, X1 gives you the percentage of information that is index but Copernic gives a very detailed description of what file / folder it is indexing. Filehand disappoints as you have to refresh the view to see what has been indexed so far.
Searching Capabilities: Again, all of them perform equally well in this category, all support boolean expressions. X1 website has a detailed set of syntax rules for search. In Filehand, you have to press Return to begin search while in X1 and Copernic, the search happens as soon as you type something in the search box. The Filehand style may be good for old computers which have less processing power.
Result Preview: Though Filehand tries to give you the result in a Google like format, I somehow didn't like it. Also, all my macros and formulae in the Excel sheets were displayed as text in the results which was very disappointing. X1 has a very nice preview pane and the rendering of documents is close to perfect. It color codes the search keywords much like Google does. Even Copernic does a great job of rendering. However, Filehand gives you and addition capability to see more / less excerpts of the results at the search result pane.
Final Verdict: X1 is a clear winner. They also have an active support forum which comes with an RSS feed. If you are tight on budget, go for Copernic. It is free and does the job beautifully.
P.S. I didn't have a chance to review other popular tools like blinkx and hotbot. But they look promising. I think we will have a plethora of search of options before the much publicized Longhorn is released in the market.