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However, whereas Munster had run away with the Celtic League the previous season, it was reigning European champions Leinster who walked the regular season this year.
After 22 games they were ten points clear of 2009 champions Ospreys and a further four points ahead of provincial rivals Munster.
Glasgow Warriors rounded out the top four while Italian new boys Aironi continued to struggle at the bottom of the league, improving on their debut season but still winning just four games.
In the semi-finals Ospreys out-scored Munster, by five tries to one, to ease into the final and Leinster edged out Ospreys in the other play-off game.
The Welsh province met Leinster in the final and it was a classic, Sean Holley's Ospreys side scraping past Joe Schmidt's Boys in Blue by the odd point in 61 to claim their fourth Celtic League title.
Early winners:
Ospreys fired an early warning shot across the bows of all the other Celtic League teams by winning their opening six games - particularly impressive was their 27-3 drubbing of European Champions Leinster on the opening day.
Leinster had a mixed start, winning just two of their opening three fixtures, with a Round 3 loss to Glasgow Warriors adding to their first day defeat - their season would soon be on the up though and they would lose only once more in the campaign.
While Ospreys got off to a flyer, reigning champions Munster were not far behind, winning their first four fixtures, beating each of the three other Welsh regions in the process.
Both of the Italian sides struggled in the opening matches but opened their win accounts in Round 4, each emerging victorious against Scottish opposition.
Glasgow Warriors' lost at home to Benetton Treviso and their early season form did not suggest they would go on to make the semi-finals, but they managed to turn their fortunes around after three losses in the opening four games.
The run-in:
The top three's positions in the semi-finals were all secure heading into the final round of fixtures but the final spot was still up for grabs.
Ospreys won their last five league fixtures while Leinster won their final four, their only defeat coming in Round 18 to their Welsh rivals - a theme to be repeated in the final.
Glasgow Warriors, Scarlets and Ulster all went into Round 22 with a chance on grabbing the final semi-final spot though, and it was the Scots who won out.
Ulster lost to Munster and while Scarlets scored a bonus point victory over Cardiff Blues at Parc y Scarlets, the Warriors victory over Connacht was enough to see them hold onto fourth spot.
Aironi's spot on the bottom of the table was confirmed long before the last round of fixtures but their final day loss to Ospreys would turn out to be their final ever Celtic League fixture as the Italian Rugby Federation would revoke the club's playing licence before the start of the next season.
Their counterparts Benetton Treviso finished the season with defeat at Edinburgh but they had already done enough to finish above the Scottish side.
Newport Gwent Dragons, Connacht and Treviso would all finish the season on seven wins but, just as the season before, the Italians would finish in tenth due to points difference and the number of bonus points accumulated during the season.
Scarlets' fifth place matched their performance from the following season but Ulster, who made the semi-finals in 2011, could only finish sixth.
The remaining Welsh region, Cardiff Blues, finished firmly entrenched in mid-table, as they had been in 2011 and throughout this season.
The play-offs:
The semi-finals went according to league positions but the nature of the individual games did not match expectations.
Munster and Ospreys, split by just four points in the regular season, played out a one-sided affair at the Liberty Stadium as Dan Biggar racked up 25 points by himself.
Kahn Fotuali'i, Hanno Dirksen, Andrew Bishop and Rhys Webb all added to Biggar's try as Ian Keatley's ten points were all Munster could muster and Ospreys ran out 45-10 winners.
The other semi-final was a much closer affair with Leinster beating fourth-place Glawgow Warriors 19-15 at the RDS Arena in Dublin.
Dougie Hall and Stuart Hogg both touched down for the visitors with only Dave Kearney crossing the whitewash for Leinster.
The difference came from the kicking tee though as Glasgow were left ruing two missed penalties from Duncan Weir with Jonathan Sexton's four successful penalties taking them into the grand finale.
Both sides scored three tries, Isa Nacewa and Shane Williams each touching down twice for their sides.
Williams' second, in his final game for Ospreys, was the crucial score though with just two minutes remaining.
Trailing by six points heading into the 78th minute, Williams scored an emotional try to bring them within one point and Biggar stepped up to convert the pressure kick and give Wales hero Williams the fairy tale send-off he deserved.
Top Scorers:
Along with the league table, the leading scorers charts also had a familiar feeling to them.
Ospreys' Biggar, still just 22, beat his previous season's tally to rack up 257 points - 59 ahead of his closest rival, Warriors' Duncan Weir.
And while Edinburgh struggled in the league table their superstar winger Tim Visser had no such trouble crossing the try line.
Visser had scored 14 tries in 2010-11 and backed that up with 13 more this season, three clear of Alex Cuthbert's tally for the Cardiff Blues.
Munster, Leinster and Ospreys players filled up the rest of the top five try scorers with Simon Zebo, Ian Madigan and Hanno Dirksen touching down eight, seven and six times respectively.
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