You also have to think about the cost of hosting, maintaining, monitoring, etc. Usually a service fee by a provider is much smaller than the cost of doing all this yourself. Of course there is some inflection point where it may be cheaper to do it yourself. And during development and while you're still small, most service providers offer a generous free plan.
> Because my desktop screams while my net connection is so so.
Can't argue with that one.
> Because a native UI kicks the sh*t out of any web interface, in looks, perfomance and integration.
Totally agree. Like I said in the post, I still write my code locally.
> Because I am paranoid and I like my data in MY local net.
Are you paranoid about your development data?
> Because I do not mind a bunch of (easily scriptable) installs.
...
> I short because the technical problems I am trying to solve go way beyond a trivial LAMP app...
I would argue that this is a good reason to you use services since they will deal with all the hard stuff of running these non-trivial services. The more complicated your application, the more value you'll get out of using services.