I just read this comment on eurogamer.net:
Guys, If you have (or plan to get) Hitman 2, do yourselves a favour and do the following when the games go live.
1) Download Hitman: The First Season. If you can, just download the launcher/Paris and not the other files.
2) Launch it (just to be sure)
3) Close it and load Hitman 2
4) Use the tile on the mode screen that mentions the first season
5) That will take you to the PSN page for the legacy pack
6) "Purchase" the pack, it should be free because you've validated your season 1 purchase.
7) Download the map packs
8 You can now play the Hitman 1 levels in Hitman 2, complete with engine enhancements (i.e. mirrors) and being able to use Hitman 2 unlocks in the Hitman 1 stages
You do lose a couple of challenges for XP but I think the ability to play everything in one "app" and the enhancements makes up for it. If you play season 1 "as is" then your progress doesn't carry through to Hitman 2, so it's worth considering to do it this way.
--
But apparently, you don't even need a Hitman 2 disc. You can just download the Hitman 2 Prologue from the PSN and play the game that way. It's nice to have your progress from the first game carried over to the second game.