These sorts of television shows communicate messages similar to those that more "babyish" shows communicate, but the context is geared towards teenagers and pre-teens. If you watch a typical "My friends Tigger and Pooh" episode, you might see a message along the lines of "be true to yourself", such as the one in which Tigger thought he was a different species and quit being "a Tigger". On the other hand, if you watch a typical Hannah Montana show, in which Hannah or Lily or some other girl/boy tries to get a kid from the opposite sex to like him/her, you'll get the same message - "Be true to yourself/don't act like someone you're not". There isn't really much difference in terms of the triviality of the messages, but what's different is the context.
In a typical Hannah Montana episode, you'll see girls going after boys in a "love at first sight" manner, and in the end realize that it isn't worth it, but only after kissing and hugging, and "sexy stuff". But in "My Friends Tigger and Pooh", that message will be conveyed through fun and, well you know, "so-called kids stuff". Basically the idea is that Disney wants to have a catalogue of shows for all ages, but that, in order to keep the parents "happy", they need to show that they want viewers to learn something rather that just get more money.
The context/message interplay is one that I've already discussed, so I'll get into a description of the content of these shows. Basically, in "Hannah Montana", there are two parallels within the show - Hannah Montana and her life (perhaps with Lily and Olliver), and her brother and Rico with their life (again, perhaps with Lily and Olliver). Now, only until the third season, Lily and Olliver were "just friends". Now, you see them flirting all the time, and you might also see Hannah flirting with boys at school. The show depicts teenage life, really, and a bit more. Only the context of the show, that Hannah leads a "double life" is of some significance. It's one of those shows when, if you cut out the flirting, you'll get a reasonable entertaining program which little kids might like to see.
Another aspect of the show is the kids that act on it. Perhaps the most controversial is Miley Cyrus. Unfortunately, Miley has been involved in several scandals; one in which she participated in a "vanity fair", another in which she did a "pole dance" or something of the sort, and another in which she allegedly sucked a guy off (kids, if you're reading this, just ignore it). And perhaps most unfortunate of all, if you google her name, you get "near-naked" pics of her, and all these scandals will come up. Therefore, perhaps parents shouldn't let their kids get into googling her name, because almost always the search will lead to some thing "sexual".
That said, the show does have many positive messages, and it may be alright for kids above 12 to view it. I would say that kids from 10-12 shouldn't really see it, because there are some aspects that can be a bad influence on them (once a guy on the show made a joke about sex). However, even if you don't feel comfortable in letting your kids view it, remember that more than 300 million people worldwide (possibly up to 500 million) have viewed this show, and more that 60% are kids, and 30% are kids below 10. So I'm sure it can't be that bad. If you're really skeptical about letting your children view it, then that's OK because they're other shows like "Wizards of Waverly Place", "Sonny with a Chance" and "JONAS" which have less flirting. Unfortunately, all non-playhouse disney shows have some flirting in it, mainly because they want it to appeal to older audiences. Hope I've helped!