I can’t remember the last time I disputed whether "different" should always be followed by "from" or whether there were cases where other choices are legitimately possible.

Personally, I have always been a strong supporter of "from" and nothing else.  My justification goes like this:

Case 1:

a) A is different from B.
b) A differs from B.

Case 2:

a) A is different to B.
b) A differs to B.  (Uh?)

Case 3 - differs from case 2 in that "than" is used in preference to "to".

What say the rest of you?

The AHD has an interesting usage note at different.

Different from and different than are both widely used, but the Usage Panel has a strong preference for different from. This is especially marked when different from can be used without inducing wordiness (when it is followed by a single noun or pronoun or by a short phrase or clause): This illustration is different from that. This was different from what we expected. In the first example, only 11 percent of the Panel consider the alternative different than acceptable; in the second only 17 percent would accept different than. But different than has wider acceptance, as an aid to conciseness, when the passage that follows is a clause (frequently a shortened or elliptical clause): How different things seem now than yesterday (acceptable to 44 percent). Here different from could not be used except ponderously; consequently the alternative to different than is to rephrase completely. Different to, a third form, is principally British. In an unrelated but common construction, different is superfluous: Three different doctors examined him.

I’ve just checked up to find out which is considered correct here.

The general rule is that we follow British usage, so that would make our form different from or different to (according to my linguistics notes, anyway).

The OED offers the following note:

‘There is little difference in sense between different from, different to and different than, and all have been used by respected writers.  Different from is traditionally held to be the correct collocation, and is by far the commonest in written evidence; different than, which is often criticized, is largely restricted to North America.’

I would be interested to hear what an American edition of OED makes of all this.

From my The Oxford Encyclopedic English Dictionary published in the US:

different ... adj. 1 (often foll. by from,to,than) unlike, distinguishable in nature, form or quality (from another) Different from is generally reguarded as the most acceptable collocation; to is common in less formal use; than is established n US use and also found in British use, esp. when followed by a clause, e.g. I am a different person than I was a year ago. 2 distinct, separate; not the same one (as another). 3 colloq. unusual (wanted to do something different).  ...  

All the best,
Barnett

The thing I was taught about differing is that it represents a divergence; the difference is between, i.e. away, ergo ‘from’.

Bryn

"Different than" by itself sounds absolutely bizarre to me in most of these cases; in the case of How different things seem now than yesterday, it sounds alright to me, but as a shortened form of ‘How different things seem now than they did yesterday’

My ear says no. "How different things seem now than yesterday," or "...than they did yesterday," or "...than they seemed yesterday," none of these can work, to my ear. What is meant is, "How different things seem now from the way they seemed yesterday," and that’s a bit awkward, and it’s certainly longer, but that doesn’t make "than" right.

"The light is different. It’s brighter than it was yesterday."  "Than" is for comparison, but not with "different."

What I meant to say is that I don’t consider ‘than’ part of the grammatical construction of ‘different’, but a part of a sentence in which there is comparison, which just happens to be one in which a construction with the word ‘different’ in it occurs. ‘Different than’ would not be a legitimate construction to me, except as an abbreviation of a phrase in which ‘than’ would otherwise occur - grammatically, rather than idiomatically.

I found this interesting note at Alt-Usage-English.org:

"Different from" is the construction that no one will object to.
"Different to" is fairly common informally in the U.K., but rare in
the U.S.  "Different than" is sometimes used to avoid the cumbersome
"different from that which", etc. (e.g., "a very different Pamela
than I used to leave all company and pleasure for"—Samuel
Richardson).  Some U.S. speakers use "different than" exclusively.
Some people have insisted on "different from" on the grounds that
"from" is required after "to differ".  But Fowler points out that
there are many other adjectives that do not conform to the
construction of their parent verbs (e.g., "accords with", but
"according to"; "derogates from", but "derogatory to").

  The Collins Cobuild Bank of English shows choice of preposition
after "different" to be distributed as follows:

               "from"  "to"    "than"
               ——-  ——   ———
U.K. writing    87.6    10.8     1.5
U.K. speech     68.8    27.3     3.9
U.S. writing    92.7     0.3     7.0
U.S. speech     69.3     0.6    30.1

And I also found this smart remark on another website:

Americans say "Scuba-diving is different from snorkeling," the British sometimes say "different to" and those who don’t know any better say "different than."

My personal recollection is that I change the usage depending on the context, although I can’t think of any particulars at the moment.

The Prentice-Hall Handbook for Writers, circa 1964, has this to say on the subject, in section 40g Use words and phrases idiomatically:

Differ about, from, with

We differ about our tastes in clothers.  My clothes differ from yours.  We differ with one another.

Different from[sup]*[/sup]

Our grading systgem is different from yours.

[sup]*[/sup]Different than is colloquially idiomatic when the object of the prepositional phrase is a clause.

FORMAL     This town looks different from what I had remembered.

INFORMAL  THis town looks different than I had remembered it.

"Different to" is not listed.  Well, this is an old American grammar book.  And I tend to be Informal a lot.