From a commercial perspective, where a new or novel idea provides a level of differentiation that defines potential for success, I can understand, and even support (The FOSS angel sitting on my other shoulder is cursing at me atm) the decision to have some closed components in a "package" that includes hardware, drivers, os and ui.
The level of support through bug reporting and the speed at which fixes are pushed, will determine how much of a problem they present to an end user (not talking devs here).
For many here, the biggest gripe about the closed components with Fremantle, related more to the delay in bugfixing (let alone all the WONTFIXes) than the challenges these components presented when devloping via the sdk.
Jolla, to all extents will aim to release a device that is as open as possible, while still protecting any IP relating to aspects of 3rd party hardware and their own IP that they see as being marketable/profitable from a commercial perspective.
This model is not really any different from that used by Nokia on the N900 or N9 and it certainly didn't stop me from lining up and buying either of these when they were released, not for what they couldn't do, or didn't have, but for what they represented and it won't stop me from buying a device that Jolla releases if it is available in my market.
It certainly represents a whole lot more than what exists on the market right now.
I certainly like the idea of a visual alert notifying of cpu/memory hogging processes. With the N9 as a reference,the app in question could glow or have a red tint in the running apps screen. Having a "top/htop" balloon over the individual open apps in the running apps screen would be good, adding a "nice" button to click on when long pressing each app would be good too.
This is the sort of thing that could be enabled in a "developer mode", leaving a minimalist view for the average user and yet still being available for power users.
Given how the swipe UI is so intuitive, I look forward to what the Jolla team can deliver, whether it's a completely different UI or just building on the concept.