In the month of the most important European elections in living memory, it's fitting that 10 EU member states mark a decade in the union.
It would be wrong to say they're all celebrating the anniversary, because while most have enjoyed benefits as EU members, some view the past 10 years less than favourably.
But with the UK electorate torn on whether they wish to remain a part of Europe, it's helpful to have the milestone on which to reflect on how more recent additions have fared.
The class of 2004 was Cyprus, Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia and Slovenia.
Uniformly, each of these nations can report a huge growth in individual wealth. In the Czech Republic and Lithuania, GDP per capita has almost tripled in the intervening decade. It's more than doubled in the majority of the other states.
But politically and economically, each has trod its own path and 10 years on, find themselves enjoying (or not, as the case may be) vastly different relationships with Brussels.
Of the 10, Poland has arguably the most amicable ties with the rest of Europe.
When EuroMaidan took to the streets in Kiev to demand Ukraine accession to the EU, they cited the example of Poland. When the Iron Curtain fell, Poland and Ukraine's economies were roughly the same size. Poland's is now more than twice the size of Ukraine's, with the average Pole taking home a pay-packet seven times fatter than his Ukrainian counterpart.
Poland was the only EU member not to enter recession through the global financial and Eurozone crises. Most EU watchers attribute this to its wise use of EU funds – between 2007 and 2013, Poland banked £56bn in EU funds, which it pumped into infrastructure projects, helping keep its economy more buoyant than those around it.
"That's something other EU countries can look to," Daniel Kaddik, the project director for Southeast Europe at the Friedrich Naumann Foundation, a liberal think-tank, tells IBTimes UK. "They used subsidises well, especially from 2009 to 2013. There was something almost Keynesian in how they used the EU money through the crisis – it kept them going."
The country is one of Europe's most stable, both economically and politically. "There are some economic statistics to quantify it, but it's basically had the most stable GDP growth of any economy in Europe and that stability has been invaluable to it," added HSBC Poland's chief executive John Rendall in an interview with IBTimes UK.
For companies looking for an offshore option closer to home, Poland is often top of the list, while its border with Germany has been a big factor in the near 600% rise in monthly exports since the year 2000.
It's no surprise, then, to see that the EU is more popular in Poland than almost any other European nation. According to a recent poll by the Pew Research Centre, 72% of Poles favour the union, compared with 66% of Germans, 52% of Britons and just 34% of Greeks.
Of course, there are voices of dissent. The anti-EU New Right, headed by self-styled monarchists Janusz Korwin-Mikke is predicted to win 6% of today's vote by the Centre for Public Opinion Research.
But that's small fry compared with the likes of Hungary, where right-wing president Viktor Orbán has been in power since 2010. Some say he has spent the four years since turning the country into a dictatorship.
Just one-third of Hungarians support EU membership. In January 2012, 100,000 took to the streets of Budapest to demand an exit. In the recent Hungarian elections, anti-EU, anti-Roma and anti-Semitic party Jobbik took 20.8% of the vote to become the strongest far-right party in the EU.
"Hungary has developed differently to Poland," says Kaddik. "There isn't more free market, but less free market. The political developments are worrying. They did a good job economically before Orbán was running the country. The problem is, at a certain point politicians in Hungary got drunk on power. It's a case of domestic politicians not being able to transform the benefits and money of the EU in a proper manner."
Cyprus is another example of a country in which the European experiment has, to an extent, failed. Upon accession the country was overly dependent on three sectors: financial services, shipping and energy. When the euro crashed, it found itself far too exposed, with no other industry strong enough to save it.
It's been suggested that some of the 2004 group wasn't ready for full integration into Europe – a case that can certainly be made for 2007's entrants Bulgaria and Romania. It's an open secret in the corridors of Brussels the pair were admitted after intervention from France, which was keen to add to its group of partners in key votes.
The next group of EU members
Serbia and Montenegro look to be the most likely next entrants to the EU, with Albania hoping to follow. But none are in a similar position to emulate Poland 10 years ago. Both economies are still relatively nascent and unprepared for the types of reform the EU would demand from a member.
Politically, an argument can be made that admitting Serbia, Montenegro as well as the rest of the Balkan states would lead to greater regional interdependence and, thus, the necessity of political harmony.
"It's self-survival. The EU is built around the Western Balkans. If there were ethnic problems again the whole region would suffer. You're in danger of having a black spot for trafficking and unrest in the centre of Europe," Kaddik says.
But none are in a position to emulate Poland in 2004. The country had 500 years of strong political and economic history under its belt before the Second World War. It's geographically at the heart of Europe, with its border with Germany giving it access to the continent's most important market.
By the time the EU came calling, Poland was ready: it had reduced its debt to GDP ratio to 60% by inserting a clause into the constitution which made it illegal to exceed this.
The planets were aligned. The country was adaptable, open to reform and is an example of the transformative potential of EU membership. But it seems that Poland was one of the exceptions, rather than the rule.