I can review the show itself in five words; it's the best comedy of all time.
This review is for those wondering whether or not to buy this so-called definitive edition, and what sets it apart from previous releases.
Well, for a start, it's bigger. It comes in one of those bookish-type DVD boxes, which has turnable 'pages' for each disc, with five in total. Series 1 takes up a disc while 2 and 3 are on two each. The real reason for the reissue of this series is the inclusion of the extra features (as well as groovy new artwork).
The set includes BBC's Ted episode of Comedy Connections, featuring all the key players apart from of course Dermot Morgan. The half-hour show serves as a great making-of supplement and deals with how the show came about, how it was initially disliked (!) and the legacy it left. Very concise and insightful, with no fluff. Also included are Ted and Dougal's in-character appearances for Comic Relief, worth watching to see them creasing up with the giggles once or twice. A two part, 40-minute interview with the creators is also very insightful, and details much of how the show was influenced, and influential, featuring some very rare footage of them performing years before the fame of Father Ted.
The only let-down of the extras is the footage of Ireland's annual "Ted-Fest", which seems to me very much like an event where people go to get drunk and shout catchphrases rather than celebrate how great the show was. All the superfluous features (sound effects, clip segments) from the original DVDs are carried over too.
In summary, I think this is the treatment Father Ted has always deserved, and the show is well worth the price of an upgrade as the extras are fantastically informative (and often hilarious) without crossing that line into having too much. I would strongly recommend buying it, whether you have the older DVDs or not (you don't? Shame).