As I mentioned in my thread about the new school, there does seem to be more issues with missing/defective parts. But the quality overall doesn't seem diminished. I also disagree that system X is less stable and durable than steck- As someone who occasionally has to cart buildings up from the basement for little girl play-time, the victorian dollhouse and steck castles are vulnerable to falling apart during transport, an issue I never have with even the largest system x buildings. I think the old steck buildings are generally more attractive, but I have appreciate the durability of X. Also, once you go through the hell of attaching all the little connectors the first time, System X goes together as quickly as steck.
I'm more concerned with playmobil becoming more stripped down, with less accessories. Some of the new themes (agents, dragon riders-even tho I love some of the sets) seem too focused on one type of play, and gimmicks, instead of more "open" themes. Don't know if that makes any sense to anyone, don't know how else to explain it... 
Initially I really liked sysX. I liked the building of it - it was fun and took time. I guess like building lego is fun.
I see now,however, how much easier Steck is for children! System x is really hard for them to put together (heck, it is for adults at times too, depending upon the individual assembly ...).
Steck only looks better because they moulded more details on the pieces. They could have done that with System X too, if they wanted. However, Playmobil would have to have diffferent moulds for each theme. This way, with just plain blob block shapes they just use the same mould and put in a different colour of plastic. No texture, no detail.
Well, they say, let's just put a sticker over it....
I do not know if one is any more durable than the other - but I have had my school fall apart on my as I tried to pick it up. That's wasn't fun - I had to take the WHOLE thing apart and start again on it because of how system X goes together. Just a pain in the ___. System X building are always falling apart around here and I know the girls do not play harder than a boy would. Nor harder than I and I have my olde toys from when I was a kid and my kids still use them.
All the nostalgia of Steck aside, I really do think System X could have been made MUCH better by having moulded in details instead of so many blank walls. The castle pieces have some stone details, why not wood planks instead of just brown coloured pastic? Then you could have red and white coloured wood pieces for barns and stables, etc
