To answer a few questions:
Yes, you can have a spare battery. Not necessarily at home, the scooter has a place where a second battery can be stored in (but is not connected). You can have as many as you want, the only downside is a 500$ deposit, which you have to make for each (you can get the cash back any time at the office. Simply drop your spare there and get the money back). When I bought the scooter, this was one thing I wanted to get as soon as I have funds for that. But now I am driving without for about a week and I realized, that it is not necessary. Due to the Flatrate I simply swap every day on the way back home, regardless of the level - I had never been below 40% (the given 80km are maybe possible on empty roads, but driving in the PP stop-n-go traffic, 50-60km are fine).

Yes there are more powerful scooters on the market but 1) not (yet) available here in Cambodia and 2) due to Oyika uses LiION technology, the battery is very lightweight, compared to what you would have to expect when having the same capacity in lead acid. Less weight, less power needed...

That thing with "trade in and get a new bike" is only for those people, who don't buy cash and use the monthly rate (which is effectively calculated about 8$ more a month).

Yes, the 29$ a month for swaps sounds much, even to me. But there are other options like no plan at all (pay 2$ per swap), 5 swaps per month (9$) or 10 swaps per month (15$). If you have used them up, simply book the next package. Not as cheap as self charged, but Google the price of a 60V/20Ah LiION battery, which will be needed in about the same frequency like the ones in your smartphone
(1½ to maximum 2 years or if you always take care that you never charge above 80% and never discharge below 40%, then the battery would last for 6-7 years, but be honest: would you do that?). For me, this worry free about the battery and having no opportunity to charge it at home anyway (no power plug available) is the best solution.

Whops, missed that one:

SternAAlbifrons wrote: ↑Thu Jul 25, 2019 1:34 pm A couple of Q's,
i/ Are similar scooters available on the open market?
ii/ Are they likely to make similar rapid advances in technology and cost reduction as in most other green-tech products?

Thanks.

i/ Not (yet) in Cambodia. There is another dealer for electric vehicles in general (cars, Taktik, 3wheeler, bikes) about 500m away, but I named the problems with that one already except that I forgot to list, that they (even the boss) speak no English at all
ii/