Agree. Jolla has to give something truly innovative and revolutional to truly attract consumers after all this long waiting.
Otherwise, the device will be ignored, like BlackBerry 10: it has Swype-like interface, business-oriented features like usual, but it doesn't gain BlackBerry new consumers - at most, it protects the company from losing its usual customers, business men.
The fact is, with world-wide economic crisis continuing, people would prefer to continue using their old phones. They can make and accept calls, include a game or two; there is no need to buy a shiny new toy if it is not much different from the old one.
Waterproof and shockproof smartphones may get a modicum of interest from the public since the concept of invulnerable and comfortable-to-use device is both tempting and unattainable.
The Jolla's concept is revolutional. Imagine: by changing the other half, you switch from private-contacts, and memory with private documents, to business-contacts, and memory with business documents.
You can have as many "other halves" as you wish, enabling ultimate information security. It's like exchanging microSD cards - only much easier to use, since microSD cards can be lost or confused easily.
Many people probably mentioned it earlier: to maintain customers' interest in the phone, they release this information slowly. Also, they release hardware information only after securing contract with hardware manufacturer, to avoid ridiculously high prices from these mongers.
Now... Who remembers MobileMind, an N900-program allowing to control a robot-car through bluetooth, with artificial intelligence to follow colour-marked route? Bluetooth uses a lot of power, as any wireless technology. Now imagine that a toy-car, or toy-helicopter, or toy-hawk, instead of being radio-controlled, has interface to be attached to Jolla phone as "the other half". With appropriate application, you can have mobile artificial intelligence. It would have one-or-two cameras and wireless connectivity (cellular, radio, WirelessLAN, Bluetooth) and speakers-microphone of Jolla phone, it would have wheels of whatever other half you attached, it would probably be waterproof...
It would be ultimate runaway phone. The owner would have to ask a passer-by.
And the passer-by would answer.
I expect that Jolla will manufacture only Jolla phone and many colours of mundane-other-half. Exotic other halves would be manufactured by other companies who would have to pay to Jolla for permission to use OtherHalf interface - patents can be useful like that - and Jolla would advertise some of these other-halves by producing open-source software to interact with them.
Some possible OtherHalf ideas:
rotating camera with optical zoom which can easily create a panorama by itself without forcing the human to rotate the whole device;
hardware keyboard (different shapes of it);
wireless charging and-or large battery and-or solar charger;
optical camera magnifier and-or telescope and-or microscope;
custom car holder - even better, the whole car as OtherHalf, wholly interfaced with the phone, and driven by artificial intelligence application on Jolla phone;
fingerprint security recognition and-or heart rate and-or iris recognition and-or blood analysis (imagine: OtherHalf with medical tools for ambulanceman, with software and hardware uniquely suited for this task);
projector and-or flashlight and-or laser and-or secondary small OLED display and-or eink display;
oh, yes, weather-based chameleon would be awesome, too - only, it should have barometer, thermometer, magnetometer, light sensor, and humidity meter, to detect weather without having to use Internet.

About ports: It's possible that Jolla first got OtherHalf idea from looking at debug-service modules and thinking: why cannot these debug ports of Jolla phone be made more accessible, so that it would be easier to debug the hardware?

About expensive-cheap multifunctional-vs-profile-specific; some occasions, like geology or medicine, might require specific instruments, and having precise and computer-assisted instruments in a profile-specific OtherHalf would be extremely helpful. But yes, most people don't need such profile-specific OtherHalves, and will choose multifunctional OtherHalves. But these multifunctional devices will not include a microscope-or-whatever to analyse a stone and say which mineral it is made of.

Best wishes.

Since Jolla will grant franchises on OtherHalf to other companies, the resulting concepts will be created by a committee of the most successful companies, and the final products will be an Arabian or Bactrian camel, a dromedary, a llama. And it will be all the better for that. In my opinion, the proud and hardy camel is better than a well-groomed horse.