If you will accept a contribution from a European who writes on wine and uses different points systems to the 100 scale, I would like to add a few remarks.
Firstly I do not think that one should focus so much on the numerical aspect of wine ratings, although it is quite right to discuss their advantages and disadvantages. These numbers do have a function, and perhaps even a use, but I would suggest that attempts to describe a wine and the pleasure (or otherwise) that the taster gets from it are of more use to a reader than a points rating. Indeed, although not a reader of The Wine Advocate, I understand that this is also Parker's position. But the fact is that points, unhappily taken out of their context (ie the comments on the specific wine and even the peer group against which it is being judged) are now engrained in the consumers mind and it is not going to be easy to remove them.
A very interesting article by Professor Barry C. Smith recently appeared in Issue 21 of that excellent (in my opinion the best) magazine,The World of Fine Wine. Entitled "Is a sip worth a thousand words?", it is based on a paper that was presented at the 3rd International Conference on the Philosophy of Wine, and debates the pertinence and function of tasting notes. Although it speaks much more of words than of numbers, the latter are mentioned, as the following quote illustrates: "As for the arbitrary and personal nature of evaluations based on numbers, we should not get too carried away. Remember that the men who invented the numbers still produce detailed tasting notes to justify their scores. So while consumers tend to discard everything except a number in the 90s, the scorers are required to display their workings to tell us how they arrived at their results."
Personally I use, like most fellow Europeans, a 20 point system to add marks to my comments. But I would not go very far to justify this, except to say that it is based on habit of scholastic markings, as indeed is the 100 point system on your side of the Atlantic. I really think that I would prefer no points at all, or a 5 point system, so fine, so variable in time, and necessarily subjective can the distinctions between wines of similar type and quality levels be.
There is much more to be said on this issue but I have already probably been too long. Perhaps we could agree that points and words are, to some extent, complementary. Words being an honest (hopefully) attempt to transmit a blend of knowledge, sensation and emotion; numbers being a (probably vain) way of relativising degrees of pleasure. In both cases, it should be emphasized that all is subjective, and so linked to that particular author's faculties and experience. And yet, the greater the experience and discernment of the author, the more objective elements can be introduced into the subjective judgement.