PDMWorks is great at keeping track of files (i.e. loading necessary components with assemblies) and revision control. Those two features alone make it an excellent tool. Its ability to look up files is also very helpful, as well as its "Reporting" function for generating BOM's and parts lists. (Just make sure the assembly on which you generate a report was checked in recently.)
The biggest drawback, IMHO, is that it is not as strict as it should be. Pro/INTRALINK has different classifications like "Locked" and "Intent to Modify," but PDMWorks only has file ownership. Either you own a file, or you don't, and if you don't, anyone can make changes to it. Owned files can't be manipulated by anyone, even admins, so most users don't keep ownership on files unless it is necessary. The larger the user base, the more essential it is to have rigorous procedures in place. The Vault Admin utility (which is included) can help you do that, as well as frequent communication with the users.