First of all, the way to choose a weapon/item is uncomfortable, you touch and hold the weapon/item icon and slide your finger up and down to choose, the problem is: your finger ends up blocking the names of the weapons/items, and they are so small that a slight change in your finger's position will end up making a wrong selection, and it's even more annoying when you have two weapons of the same type (i.e. the M9 and the USP). There are some improvements in special effects and the characters models, as well as the fonts used for texts, but it doesn't change the fact that most textures are still the same, so this is more like a port rather than an upgrade, I have a BC Ps3 and when playing any Ps2 game it outputs to HD resolution (if you have an HDMI cable), comparing the graphics between the Original Ps2 titles on a Ps3 and this HD versions, the change isn't that much. Another thing that bothered me was how the Cross and Circle button are swapped (Cross to select, Circle to exit), you may say: "but this is normal in US and EU", yes, but the original titles forced you to use the Japanese way (Cross to cancel, Circle to select) and, being a long time fan, I've grown accustomed to it, so when I play MGS2/3 I expect the Circle button to select and Cross to exit, now this may not be a problem except for the fact that you can't change it, and this is not the only thing you can't change, you can't change the game's language, where in MGS3S you could change the language independently of the system's language, there is very little modification to this game, not even have of the options shown in the original tittles are shown here. Which brings me to my final complaint: trophies. They are so easy you that most of them require doing something you already have to do or uncover an easter egg that was uncovered in 2001. All of this had me realise that the HD collection was targeted at new comers rather than long time fans like me but hey I'm playing it while I write this, which means it serves it's final goal: playing MGS2/3 on the go.
Update 1: After going deeper in the game I've found glitches that weren't there on the Ps2, specially with Mgs2 (lightning glitches, graphics glitches, a glitch trophy...).
Update 2: After beating Snake Eater 3 times and unlocking every possible item I've realised that there is nothing new in the game, as a matter of fact, there is less than in the original: both the monkey mask and the banana camo are missing, they removed duel mode and practically gave you the green face paint and the DPM camo "for free" but it's not the same for the banana camo and the monkey mask. For those of you who are not familiar with Subsistence, the green face paint and the DPM camo were unlocked by beating duel mode in both normal and special, obtaining 1st rank in all of the bosses. It was a really hard task that awarded two really cool items, but now you don't have to do sh*t to get them.