Summary: If you want a good tool for solving or setting advanced cryptic puzzles, or you already cart a lap-top around and want to do some advanced puzzle solving on the train, it's a gem. But if you want a well-designed CD-ROM version of a dictionary, this is not quite it.
If you don't understand my fairly curt description of the features, have a look at the full details on the Chambers web-site.
This CD-ROM contains the complete text of the 2003 edition of Chambers, plus what I assume is the full text of Chambers Thesaurus (I don't have a paper copy as I strongly prefer the 'topic number' style of thesaurus to the 'alphabetical' style chosen by Chambers). The various introductory sections and appendices from both books are also included, though they're not searchable in the same way as the main sections. Installation is pretty straightfoward, and you get a short printed user guide which explains things quite well. The whole thing is installed on your hard drive, so you don't have to find the CD as you do when you want to use Microsoft Encarta. At present, you have to order a CD from Chambers - youu cannot download the software and buy it on the web, even though the files would only amount to about a 40Mb download when compressed.
There is very little in the way of linking between dictionary and thesaurus, so they're best regarded as two references that happen to share a CD and user interface. As you'll see from some of the comments below, there are various points where user testing could have identified problems with the CD's user interface. If these had been addressed, the CD would have been a far better product.
This offers two look-up methods - an alphabetical list, and a full-text search. Using the alpha list is just like looking up entries in the paper version. There's a limitation that also affects the dictionary, and matters more on CD-ROM than on paper. Words with multiple meanings like 'present' just get multiple entries with superscript numbers in the 'index' list - 3 of them in this case. In a paper dictionary this causes little trouble because you just scan the various entries. Here, you have to click on each one until you find what you're after. These would be far more helpful if they included some hint about which was which, like present1 (here), present2 (donate), present3 (gift). Alternatively, the word list could contain just one copy of 'present', and clicking it would display the text for all 3 dictionary entries in the same display pane. The alternative thesaurus search method is called "full search". This looks for all entries containing the search word anywhere in their 'synonym list', and displays them in a "result" pane where you can click on each one and see the entry, with the search word highlighted. In practice, using full search will often give you the range of synonyms you can get from intelligent use of a 'topic number' thesaurus, rather than the often rather short list displayed by using the alpha search.
Alpha and full text searches are available again, and so are searches for patterns like prese* or ban??a and anagrams of the search word. There's the same problem with numbered entries. For a word like port, you could get pretty frustrated, hacking through the 8 different lucky dip choices. Pattern-matching searches only return a maximum of 127 results, and there's no option to display the next 127. Full-text searches will return more results, but there is a limit, and fulltext and anagram searches don't show a number of hits.
There are some quite intelligent features, like the pop-up pronunciation symbol guide that displays if you click on the pronunciation. But sometimes things are less smooth. Double-clicking the "OE" in the etymology for port1 will display the 'oe (same as oy)' version of 'oe', not the OE=Old English one, and double-clicking the Latin word "portus" in the same etymology will display the entry for "porous".
You can achieve quite a lot with the full-text search - if you know that a word comes from Spenser, you can get a list of all such words. You can use some advanced search techniques, so a fulltext search for 'brass AND slide' will find 'trombone'. But you can't search for Spenserian words beginning with 'emp' except by scrolling in the index list, and searching for a Spenser/?m??yr? word is impossible. And things that look possible like searching for words marked as 'obsolete' or 'offensive' become frustrating when you find out how many similar labels are used - "offensive", "derog", "vulgar" and "taboo" for example. This is an area that needs cleaning up in the actual dictionary text, before a CD-ROM version can be really useful.
The 'Print' option is not worth wasting paper on unless you want to produce something big enough for use on an OHP.
You can scroll forwards and backwards through your recently viewed definitions, but only one step at a time. A history list as provided in umpteen web browsers would have been much better.
The settings dialog has various user interface howlers which I won't bother you with. On the functionality side of settings, it's rather odd that all the same font size has to be used for all the display panes - I'd prefer a bigger font for the one where the actual dictionary entries are displayed. If you don't like the colours used for different bits of the dictionary entries, hard luck.
Various people have reported problems with license keys - confusion between letter O and figure 0. You may need to hassle Chambers if it happens to you, but try assuming they're all zeroes first.
There's a pop-up version supposedly for use with apps like Word, but no real integration. You can create user dictionary/thesaurus entries, but you can't set up the same formatting as for the real entries, or integrate your stuff into searches, so this seems a fairly pointless exercise.
For some reason, starting up the CD application takes about twice as long as cranking up Microsoft Word. This seems unnecessarily slow. Also, the application has crashed a couple of times after a lot of searches. I'm told that Chambers are supposed to be releasing a patch for this problem in about December 2005.