I think I missed the real meat in this comment in my other response, so here's attempt #2:
> So from European point of view those "lots of useful tools to solve problems with the computer, based on a wide ecosystem." are nowhere to be seen.
These "useful tools" are web sites (and web apps). By providing excellent support for these, the devices are immediately useful. Much better than hoping that another ecosystem like Android's can be jumpstarted.
The average user buys a (hypothetical) Dartbook: Looks for some Dart app. Gets frustrated by the lack of choice. Returns the device.
The average user buys a Chromebook: Browses their favorite websites (and face it: 90% of contemporary computer use is _just_ _that_). Reasonably happy customer (unless they insist on installing "TuneUp Utilities" because they always do that).
That's what I meant with the availability of lots of useful tools to solve problems with the computer (in that case, a Chromebook), repurposing a wide ecosystem (the entire web, basically).
From your other comments on this site (eg about the Atom editor), you seem to be fundamentally opposed to html/js as a platform and with that sentiment, Chromebooks must look anathema to you. Alright, that's one position to take.
But what use would be a Dartbook to you? You'd probably complain (with full reason!) about its inability to run emacs just the same.