Have to say I was extremely impressed. The aspirations that they have for their kids were just as I would hope. They are keen to ensure that kids gets good Higher results first time because that is what the Universities are really looking for. If kids stay on for 6th Year (as many do), then it is to widen their knowledge (or apply for Oxbridge) - and allows them to get unconditional offers (as one kid has just done for Medicine at St Andrews).
(BTW: the two kids who got conditional acceptances for Cambridge a couple of years ago, did go there - for whoever it was who doubted that their conditional acceptances meant that they succeeded in doing so).
The pastoral care seemd really good and they work hard to ensure a smooth transition from primary to secondary. The head of maths talked about how they work closely with the primary schools and then in the first few weeks of term to establish what level the kids have got to to ensure that they continue to be stretched and enthused (the example he gave was if a child is said to have "passed level x" - have they only just passed it and maybe still need consolidation on some elements or did they pass it a while ago and are ready for much more advanced stuff). They want to ensure that kids coninue to maintain the momentum from primary school.
The head teacher talked of importance of sport in instilling discipline and focus in the kids - that partly why she has introduced rugby to the school.
We saw an S1 drama class in action: the teacher talked about how drama is really good to help S1s get to know each other and develop their confidence.
There is a Movie Club, they have links with the Shed (they had just been making/planning a music video across there), one of the drama teachers is involved with the Glasgow (Scottish?) Youth Teatre, so they have an active drama club (they have a stage and proper lights), the new sports hall is bigger and nicer than the one at Hutchie (enormous, with a well sprung floor). They still have the original gym hall in the main school building, as well as a well stocked gym with 3 or 4 treadmills as well as cross trainers etc (donated by a business that was closing down). Plus of course, they have a swimming pool on campus.
They have a good Art Department - there were "proper" 
life drawings up in the corridor (beautifully done, I have to say) - with a description saying that Life Drawing is a requirement for the entrance portfolio for Glasgow School of Art (a number of kids have been successful in going there).
We were also told about the Wind Ensemble (or was it Concert Band? all students get given the opportunity to learn an intrument), Astronomy Club, ski trips (S1s and S2s going next month), trip to South Africa (S3s - going in May) which is part of its twinning with a school out there. Lots of extra-curricular activities.
The other thing I was impressed by was the respect with which the teachers seemed to be held - and the attention to detail but caring attitude of the teachers who were showing us around (commenting on/complaining about a kid who was wearing a blue jacker rather than the black that they are supposed to wear). Dh commented on a clean and tidy the place was - and noticed the "natural" way that the teacher who was showing us around just picked up a piece of paper if she noticed it on the ground.
One of the teachers mentioned that a close relative of hers who is currently in 1st or 2nd year at one of the Scottish real "old" universities was pissed off that his parents had sent him/her to Mearns Castle rather than to Shawlands (for various complicated reasons not to do with education), 'cos at Uni he/she has got to know a number of Shawlands former pupils and he/she felt that Shawlands offered much more than Mearns Castle. An interesting perspective from a recent pupil! :)
They were delighted that we were looking around early and gave us plenty of time to ask questions. It was also useful because they start transition process in November, running after school "clubs" for the P7s (eg Maths, Engineering, Drama) and then have a couple of mornings at the "big" school in January - all of which is before the time that you submit the placing request forms. So if they know that your child is planning on coming to the school, they can make arrangements for them to join in these activities.
The only :( is they will probably be dropping Latin by the time ds is there as the only teacher is planning on retiring and probably won't be replaced :( But German, Spanish and Urdu is taught as well as French - all the Higher and beyond (I think they have to take a 2nd language on top of French in S1)
If a kid want to do a subject that they don't offer, they will facilitate it at one of the local colleges or another school (more applicable in the later years).
The kids all seemed really polite - and concentration and discipline in classes seemed good. We couldn't really see the upper school in operation (although we walked past classrooms of S4s and S5s) as they didn't want to disturb them 'cos they are in the depths of exam revision/consolidation but the younger kids all seemed keen and focussed.