If you already own ME2 and ME3 you are far better off just buying ME1 from the PSN Store. This incomplete trilogy is missing a great chunk of DLC from the third game in particular and unbelievably a hefty sized mission from ME2 which you get with the bog standard version of ME2. Hopefully somewhere down the line they will release a complete PS3 trilogy package incorporating all the missing content. I could have understood it if this stuff was Xbox or PC exclusive but these are packs that are out there already for PS3; crazy.
At the very least the set should have included the Lair of the Shadow Broker DLC (for ME2 360/PC) the Arrival DLC (for ME2) and From the Ashes DLC (for ME3) as they are all important to the story. They have not. So if you already own all 3 games and the given DLC you may as well skip this set. Unless you have a PS3 and you want a disc based copy of ME1.