Oh, it's definitely worth it. I'm a Metal Gear fan, and I must say, I felt the nostalgia playing all the old Metal Gears, plus Peace Walker. Metal Gear Solid 2 in this game is the Substance edition, which has pretty much the VR Missions, Snake Tales, and all that. Solid 3 is the Subsistence edition, minus the Metal Gear Online, Snake vs. Monkey, and Boss Duel mode. Peace Walker is the exact port of its PSP version, and you can transfer your saved game back in forth for this game.
Honestly, if you're a Metal Gear fan, you will definitely like it. If this is your first time playing it, I really recommend getting it and playing it. There are a lot of things, achievements, titles, and easter eggs you can get in the HD collection.