12th scale has been on the up for 3 or 4 years now over here in the UK. At the tail end of the nineties, you'd usually only see a C final at a 12th scale national. When I started doing the nationals around 3 years ago, there were about 45-50 drivers at each meeting. Last season a lot of the meetings were fully booked (capped at 80), and nearly all of them have had over 70 drivers this year and last.
It seems to be a trend internationally too. The 12th scale European Championships has always been an open entry event (ie if you want to race, you can). For the first time this year, EFRA are going to have to allocate places to each country (IFMAR worlds style) because there were over 60 entries within 2 days of the booking in website opening! I think a lot of this is down to the introduction of odourless additives. The popularity in the UK has also been helped by the introduction of a 19t class a couple of years ago (we run 4-cell 19t on saturdays at nationals, and 4-cell mod/brushless on sundays)
12th scale is easily my favourite class. Unfortunately its almost exclusively a winter class over here, so I have to go and race touring cars over the summer instead.
Someone else from the UK has mentioned the lack of club racing in the UK on this thread already. This is definitely an issue, and the reason for it is basically because there are only a few indoor clubs over here that have large enough track areas to properly cater for 12th scale. You also need at least 3 heats of cars to get a decent grip line down during the meeting, otherwise its like driving on ice!
Personally I dont do any 12th scale club racing for the above reasons, and I only attend the nationals. Most of the national guys are the same. there dont seem to be many drivers who do 12th scale at club level only; unfortunately its nationals or nothing for most drivers.