Personally, I did TY so tough to give a fully neutral view. I could possibly be very positive against TY if I hadn't done it. I can only provide the details on what I felt I gained from the year as I don't believe I would have had any positives from not doing it, more down to personal circumstances than any real belief in the TY system though.
The "facilities", or options, were similiar to those experienced by SNB and ixus. How much a student may gain from them, I'd say is more down to the individual student than the school.
I did TY for one main reason, age. I had just turned 18 in the Summer following my Leaving Certificate. Without TY I would have sat my Leaving at 16 and started college having just turned 17, so TY was certianly an advantage from that POV.
What I gained from TY was far more than that...
It gave an opportunity to experience things which otherwise I never would have had an opportunity to try.
Off the top of my head the most memorable would be the first aid courses, social work (voluntary work at a local special needs school and nursary home), TY mini business (each class sets up a business and run in competition against each other - really just a bit of fun but with all profits going to charity), work experience (two school organised placements [two weeks each] and I took two other placements with the school happy to allow the time off to try them out [again, two weeks each] (one of the placements encouraged me to follow my current career and helped in choosing the course I went on to study in college - I requested the additional placements as I couldn't get a placement I desired in the time periods on offer during the set placements), part time work as a sports journalist for a local paper (the break from "study" doesn't have to mean students do nothing, it's just down to them how to spend the time for best results), Art projects (as I was a keen artist it gave the opportunity for some large projects [St. Patricks Day parade stuff, Christmas nativity scene for the school etc.]), other school activities (this does come down to individual schools, we were lucky enough to have a few pro-active teachers who encouraged participation in some of the national Science and Maths competitions - not for everyone, but whatever area a student is interested in there are activites which could be taken up)........
These are just a few of the things that spring back to mind when I thought about TY for the couple of minutes it took to type this reply. I found it a great year to follow on areas of interest which you normally don't get the chance to indulge in. 5th and 6th year have heavy workloads, then college hits so the workload increases and summers are spent earning to help pay for college, then work starts (possibly without the college) and it leaves very little time to persue these interests. It also provides a chance for students to consider what subjects to continue on with to LC and what career path they wish to continue on following the LC........ not all students will do this however, so how much can be gained from TY comes down to the student in question.
My own suggestion is to ask the child if they wish to do it. Teachers allow for a lower workload as it provides a chance for some of the activities mentioned above. If the student doesn't wish to do anything, chances are they won't be forced too and just spend the year doing as little as possible.