Right, and that is why so many docs look bad! Those metrics differ. The same for times: adobe times metrics even differ/change over time (nelson beebe has done some excellent research on this; see pdftex mail archives); this is the main reason why i stick to urw times and palatino etc. Also, they go well with math times (tx) and math palatino (px).
Even worse with some Linotype fonts: They even changed the encoding without changing the name on "Linotype Gold 6". Ok, now it's fixed, but only after some firms refused to pay their ten thousand euro licenses for a software that only causes trouble...
well, as far as i know adobe stopped adding the famous 15 to distributions; also, beware: acrobat will replace helvetica etc by the system specific preference, which of course has different metrics (arial on windows), and again, is one reason why files start looking real ugly.
No, not system specific: Acrobat is delivered with Arial, TimesNewRoman etc. even for Macintosh! (since Acrobat 4) Grüßlis vom Hraban! -- www.fiee.net/texnique/