My only problem with things like the PSN is the regional availability.
I keep hearing that Game X is available, and then I find out they mean in the US or wherever. EU tends to get different release dates, if at all.
When will companies realise that the internet is not region locked? (at least not yet)
[edit] I'm mostly annoyed about Blood Omen: Legacy of Kain. Damn thing doesn't work on the PC, and isn't available on the EU PSN.

They have all parts of Crash Bandicoot, except for second, which is the only one I actually want. What the hell? So yeah, region locking sucks and doesn't make any sense whatsoever. Everything as usual then

Well, I thought about this one, as well as some other games wich are sequels of classic games, but I don't, it doesn't really fit in ports and remakes.
Hmm... I think I have to make a new category.

I do enjoy being able to download some of the old PSX classics. I'm playing Soul Reaver, currently. It should be noted, however, these are not ports, but instead emulated versions of the original PlayStation games. Nothing is changed or improved to make them PSP versions, not even making them widescreen for the PSP screen (though it's completely customizable as far as whether you want to zoom in a certain amount or *shiver* stretch the image *shiver* or whatever... you can even shift it up or down if you only want to view a specific portion of the screen)...

It can be possible, I think, for titles using DosBox or ScummVM.
Installing games with GOG installers on the PC, taking game files, and installing DosBox and ScummVM on a modified PSP should do the trick.
Not yet tested though.
Controls might be difficult for some games, I guess.