As much as I love capitalism, there's a few differences as you go up in tiers beyond just room limits. Today the most notable is the ability to manage more than one office location. In time it will will expand since certain things (i.e. SAML, high resolution analytics, audit logs) aren't needed by the typical 5 conference room company. The more stuff you're managing, the more complex the relationships become -- not just an N + 1 operation.
It's generally not a dealbreaker for most offices. With external battery packs you can get extra days, or you could just get a free standing mount that moves closer to a nearby outlet. Most commercial buildings require power every 8 feet or so on walls, so you're rarely in a power desert.
Couple perspectives you might find interesting (I say this having to learn the lay of the land over the past year myself):
Most offices are designed with 1 conference room per 10-20 employees. If you have 15 conference rooms you probably have well over 100 employees and many millions in payroll. Those people presumably have many meetings, and the cost of not being able to get their job done is measurable.
Conference rooms can be between 200-300 sq feet, so if you have a 15 of them you're looking at several thousand sq ft on your lease. Depending on where you are in the world, that's probably around $10K/month or so in real estate.
The effective rate is about $17/month/room, which in most cases is tiny compared to the cost of mismanaging office space and productive time above.
For series 10, absolutely. Their series 20 seems to have better battery life (4 AA), but they need to "approve" you in order to purchase them... still yet to see one in the wild.
Love this. We've been working on a version of this for the office at Robin (http://getrobin.com). Biggest challenge so far has been getting interop across Android and iOS. Beacons are reliable if you have a binary "are they or aren't they here?" but a bit harder to map to smaller rooms when certain Android devices register a signal difference of 4X depending on physical orientation -- that was a fun one to figure out.
Familiar with it. It's interesting how they break down by country and make pictures the focal point of choices. We opted to go for a rapid fire approach using HTML5 History API and local storage to allow quick cycling.