Basically Mr Klaus, president of the Czech republic, defend his country's non-adoption of the euro because it has left him free to use the traditional method of dealing with recession by loosening monetary policy - with a lower exchange rate for their currency, their exports look cheaper to foreign buyers, and imports are more expensive for residents. This brings in more money (in a harder currency), keeps more of that money in the domestic economy, and also allows the government to inflate away some domestic debt as the economy improves by raising interest rates.
None of these options are available to euro members, any more than they are to individual US states. So to repair their state balance sheets in a federal monetary environment, they must make politically unpalatable like raising taxes or cutting services, and don't have much flexibility in terms of repricing their external trade. That means pissy voters and a somewhat slower recovery, because trade gains must come from either reductions in base costs or improvements in quality, both of which are harder to realize than to talk about.
On the other hand, these latter things represent fundamental economic improvements, whereas currency revaluation is something of a sleight-of-hand that taxes people indirectly and leads to inflation. But for a politician, that's highly preferable to telling the voters that they are likely to get less and pay more. So, less fun and freedom for euro-zone politicians who have to implement austerity programs and persuade their electorate to deal with financial reality, but (in my opinion) better for their economies over the longer term, as they'll make needed reforms while the Czech Republic and Poland only go through the motions of doing so and carry forward their structural problems.
Sorry that 'summary' is so long - not much of a time saving :-/