Further to my review (see http://www.boardgamegeek.com/thread/93137), I wanted to say something about how I've used this game in the classroom.
Scrabble Cards are a pretty good educational resource in a language-learning context, or at least one which calls for a less formal, more fun activity. It isn't really a language game, but contains linguistic elements which can easily be emphasised within the classroom. First of all, I usually make students spell the words as the place them, since even students of intermediate level have problems with spelling in English. It is also possible to make the student count the value of the word they have just played, and add that to their running total.
The basic nature of Scrabble as a language game need little explanation, although clearly using seven cards will put high demands on students. I wouldn't use seven cards before students of an intermediate level. Pre-intermediate level students can usually cope with eight cards, while elementary students can usually get by with nine cards. I think I have even played Scrabble with beginners, a short way into an intensive course, using ten cards to make it as easy as possible. Making words out of so many cards might not seem difficult, but elementary students can definitely have a sense of achievement from making words out of random letters, and the competitive element helps spur them to do so. Spelling and numbers can also be practiced with students from elementary level on. Of course, the category cards will prove more difficult for low level learners.
Also, because cards are removed from play and placed in a separate pile, it is easy to shuffle them back into the main pack and keep the game running until a time limit is reached, rather than until the pack has been exhausted.
Students need to be reminded that they shouldn't hold on to category cards, since otherwise an imbalance can open up between students who do and those who don't. I would generally advise removing the card which reads "2 letter word (+5,-2) | Starts with "Q" (+15, -8)" because students usually hang on to it, either tempted by the +15, or unwilling to play a mere two letter word.
Students should also be reminded that modifying a word means that it is scored again - adding an "s" to "horse" means you score the whole word again.
I also remember playing a version of Scrabble in the '80s in which letters were built on top of one another, so that if one player placed "bed", anther could place an "r" over the "b" to make "red". This variation works well in the classroom, but not with learners of intermediate or above - it's too easy!
Of course, there is no maximum level of ability for playing Scrabble with students - I often play it with Cambridge Proficiency candidates at Christmas Parties!
And I have successfully played the Scrabble Card Game with 18(!) students, in six groups of three; more than six groups, or more than three in a group in cumbersome.