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Linux, Unix, and Open Source in Poland [119]
most of open source software is created by home programmers - do-it-yourself people
Sorry I have to jump in here, most of these home programmers are not hobbyists as you are implying. I would guess that the majority of them are specialists and professionals. An example is Doug Cutting who wrote the open source Nutch and Lucene projects which are used for searching and indexing. He now works at Yahoo. To tinker with this stuff requires a lot of in-depth knowledge.
there's a smaller amount of testers
Again not sure I agree - how many people does Microsoft employee to test product X? Pick a number, 50? 100? 500? Now compare that with the potentially thousands of people who use an open source product and report back problems to the developers. The result is that the quality might be lower for a newly released product but after a couple of releases it's usually fine. But that's why open source projects usually come out at version 0.9 so they have time to incorporate feedback.
there's a bigger chance to encounter a bug
I read an academic article that talked about peer review for software once. Microsoft or other proprietary software is closed and therefore can't be scrutinised unlike open source stuff, so the logic goes that a major bug is less likely to go unnoticed in open source. That's why architects use peer review for their plans. They don't want to build a new suspension bridge and then realise later they messed up their maths somewhere...
It also might be hard to find a real gem in all the rubbish that fills sourceforge and other open source portals..
Yep, there is a lot of crap out there too. Lots of projects are started and not maintained, or badly organised etc.. But the good ones bubble to the top. But the great part is that if you have a problem with the code or functionality you can always fix it or modify it yourself (if you are so inclined), and help is usually available on the net.