Why play a Bjornaer?
I'll always talk mechanics and optimization, so I'll get to that, but first some character-oriented stuff: Being an animal-person is something a player can easily grasp as a theme that can really pull a character together. Bears and ravens and lions are real, and have deep associations to real folklore and mythology in both the modern and medieval world. By contrast, Hermetic Magic (AM style), though interesting, is total fiction and therefore kind of lacks a bit of resonance. Pick an animal, pick a congruous personality, virtues and flaws, and get a grounded character.
As for mechanics and cool stuff, losing access to a familiar definitely sucks. On the other hand, gaining access to the abilities of an animal can make it worthwhile, even before initiation. If you can turn into a bear (a favorite) without need to roll dice even in a cathedral, you have combat covered, at least for your first few years, and can then specialize in any kind of magic you like. If you prefer a more subtle animal, like a bird for flight and awesome perception, or maybe a shark or pike in a saga where water matters, those bring abilities to the table as well.
Even before initiation into Inner Mysteries, you can have the most fatigue in the Order, when in animal form. That pairs nicely with LLSM, putting you among the best spontaneous casters in the game. Alternatively (heck, additionally), if you can cast without words or gestures, then you can cast in animal form, making your magic even less obvious, giving you some fine spying options. (Who is going to blame the horse?)
With initiation, you can not only get an augmented heartbeast, but can spend time augmenting it even further with any animal quality you want (that isn't utterly contrary to your Inner Heartbeast), many virtues and (usually less interesting imo), powers. With Theriomorphy, you can use these qualities in human form. You can also gain access to sensory magic, which can be put to interesting effect.
But if you don't find it cool to play a character close to his animal nature, that's fine too, and Bjornaer is clearly not the right House for you.
EG: Hearbeast(bear), LLSM, Silent+Subtle Magic, Cautious Sorcerer, leaving you up to three virtue points. You can specialize in any Arts, and are well set up to dump all of your Art points into the TeFo of your choice, since you have both LLSM and extra fatigue to power it.