I was at Legoland last week and bought myself a new notebook. I hadn't seen it before but can see it's been on SaH for a month.
It comes with lots of 1x1 tiles with letters on, although they are with brighter coloured backgrounds than the previous black only.
It's on the Brickset database
and on Bricklink, so it may be that it's well known about, but I've seen people talking about getting letters before (for instance when the business card holder came out).
A couple of very annoying things though:
1. The multi coloured backgrounds are not entirely useful for a MOC. The backgrounds are red, yellow and lime, but a given letter is always the same colour. For example, they've made red T's but no lime or yellow ones.
2. The distribution of letters is pretty screwed up. I appreciate they probably make these items for distribution in many countries (there are a few accented letters), but it seems madness to have only one O and three Qs.
3. Individual letter tiles are all marked not available on the Replacement Parts service.
May be interesting to someone nonetheless.