Ospreys under the new leadership of Kiwi Scott Johnson, who joined them after coaching the United States national team, and captain Ryan Jones had a strong core of 2009 Lions internationals including Alun Wyn Jones, Ryan Jones, Mike Phillips, Shane Williams and Tommy Bowe.
Head coach Sean Lineen led Glasgow to a third-placed finish while reigning champions Munster secured a losing bonus point away at Cardiff on the final day to finish fourth at the Blues expense.
Connacht finished bottom but enjoyed a stronger season than many were expecting while the Dragons finishing above the Scarlets and comfortably qualified for the Heineken Cup.
The season saw 333 tries - an average of 3.581 a game - a slight decrease on previous seasons but that stat didn't demonstrate a lack of drama.
Early Winners:
The Scottish sides started strongly with Glasgow beating reigning champions Munster and Edinburgh getting a 22-21 away win at the Cardiff Blues on the opening weekend.
Both Scottish sides followed up those wins in round two with Edinburgh making it three out of three against Ulster.
Reigning European Champions Leinster, after slipping up against Scarlets in the opening game, won their next four including a 30-0 demolition of Munster with tries from Gordon D'Arcy, Brian O'Driscoll and Shane Horgan.
After back-to-back victories at home to Munster and away at Scarlets, Ospreys opened the New Year with a 26-0 victory over Cardiff.
The win, thanks to a pair of tries from Nikki Walker, sent them to the top of the league.
The run-in:
The Ospreys couldn't maintain their place at the league's summit however and by the time they played Leinster in April a 20-16 defeat moved the Irishmen seven points clear at the top. The Ospreys however would have their revenge later on.
The Welsh side bounced back the following week with their first victory at Thomond Park to significantly boost their chances of a home semi-final.
In damp conditions Dan Biggar scored all 15 of his side's points while fellow fly-half Ronan O'Gara managed a try and two penalties for the hosts.
Munster, with injuries to Paul O'Connell and Doug Howlett, did manage to secure their place in the play-offs, and a trip to rivals Leinster, two weeks later when they secured a losing bonus-point at Cardiff Blues.
Jamie Roberts scored for the Blues who needed a win to leapfrog the Irish province into the play-offs but the right-foot of O'Gara kept Munster in touch with four penalties as it ended 13-12.
Cardiff's disappointment meant the Ospreys would be the only Welsh representatives in the play-offs and they secured a home semi-final with a 42-10 win against the Dragons at the Liberty Stadium.
The home side, who fielded 15 full internationals, ran in five tries, including one for Dan Biggar who scored 22 points, against a depleted Dragons side.
Ospreys win meant Glasgow were left to settle for third place despite their own bonus-point win at the Parc Y Scarlets on the final day with Dan Parks kicking 17 points.
Leinster would also have a home semi-final after coming from 14-0 against Edinburgh to win 37-28. The defeat saw Edinburgh finished sixth in the league, ten points behind Scottish rivals Glasgow.
Play-offs:
Ospreys booked their place in the first ever play-off final after a Shane Williams try and a moment of pure brilliance from James Hook saw off Glasgow Warriors.
Williams took advantage of a rare mistake in the Glasgow backline to collect the ball and race clear to give Ospreys the lead in the ninth minute.
Hooker Fergus Thompson got the Warriors back into the game two minutes into the second half with his own try but 12 minutes later Hook dealt the decisive blow.
The Welsh fly-half gathered his own chip and chase on the left wing to cross the whitewash in a day that was a stark contrast to his opposite fly-half Dan Parks who missed eight kicks.
Leinster's top of the table finish, three points ahead of the Ospreys, meant they welcomed Munster to the RDS Arena for a brutal second semi-final.
The two Irish provinces exchanged penalties in a frantic opening half and O'Gara had given the visitors the lead before Sexton set Rob Kearney away for an all-important try.
Two further penalties for Sexton, back after a month off because of a broken jaw, saw Leinster knock the reigning champions out.
Nearly 20,000 fans packed into the RDS in Dublin for the first ever Celtic League Grand Final as Ospreys upset the odds to secure their first ever win at the RDS.
Tommy Bowe raced over for the Welsh side's first try in the 19th minute with Dan Biggar successfully converting for a 7-0 lead. Despite a Sexton penalty, man of the match Lee Byrne added a second try just before half time which Biggar converted.
Three second-half penalties for Sexton reduced the margin but Ospreys held on to secure their third title and meant Leinster's head coach Michel Cheika left without a final piece of silverware.
Top Scorers:
Glasgow's Dan Parks returned to the top of the points scoring charts after a one-year absence with 216 points.
Dan Biggar was 11 points behind with 201 despite also being able to play in the league final; Cardiff Blue Ben Blair (150), Connacht's Ian Keatley (138) and losing finalist Sexton (136) completed the top five.
Despite reaching the final, no Leinster player featured in the top five try-scorers for the year with the top prize going to Dutch-born Scottish wing Tim Visser with his ten tries.
That was two more than Tommy Bowe managed for Ospreys and Sam Danielli scored for Ulster. Fionn Carr enjoyed a strong campaign with seven tries while Aled Brew scored six for Newport Gwent Dragons.
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