Anyone try out Crash Commando from the PlayStation Network yet? It's very reminiscent of Soldat on the PC. Basically it's a multiplayer shooter set on a 2D plane but with 3D graphics. However stages have multiple planes that you can travel in between.
Right now the game modes are limited to DM, TDM, CTF, and a mode where you have to plant bombs on the opposing team's objective points.
The weapons are pretty standard fare with your usual knife, pistol, assault rifle, rocket launcher, etc. You also get to drive a few vehicles that even have rocket boosters (you also have a jet pack on foot) allowing you to ascend/descend vertically.
Crash Command isn't terribly original but it's made with polish and plays well. For ten bucks, I'm having some fun with this game.

Almost bought it, just because it looked so much like Metal Slug (one of my all-time favourites), but I just can't see myself playing such a thing in multiplayer mode... give me tons of stupid (not stupid console gamers, stupid AI) enemies running towards me and I'll buy it in an instant :)

Not very much like Metal Slug at all in terms of gameplay. You do get bots to fight against in single player mode, but it still has a very multiplayer feel to it. You'd be disappointed if you expect an oldschool arcade shooter from Crash Commando.
If you have an extra ten dollars to burn though, you could do worse. But there's still one or two titles I should have purchased on GOG before going with Crash Commando.

I think my best purchase on PSN (actually I purchased it twice, once for my PS3 and once for my PS3) was Riff: Everyday Shooter. I know it seems too expensive, but it's just so much fun.

is there anywhere with a list of all the stuf on the PSN? Not having a PS3 I've got no idea what sort of thing is out.

Give me a second, I'll just write down what I see on US and DE stores
===========GERMAN STORE===========
===PS1===
Bishi Bashi Special
Command & Conquer Retaliation
Cool Borders
Crash Bandicoot
Crash Bandicoot 3 Warped
Crash Team Racing
Destruction Derby
Driver
Everybody's Golf 2
G-Police
Hardcore 4x4
International Track & Field
Jet Rider
Jet Rider 2
Judge Dress
Jumping Flash
Kula World
MediEvil
Motorhead
N2O
Populous The Beginning
Rayman
Reel Fishing
Sim City 2000
Street Fighter Alpha Warriors' Dreams
Street Skater
Syndicate Wars
Theme Hospital
Theme Park
Wipeout
===PS3===
Calling all Cars
Gauntlet II
The Last Guy
Mega Man 9
Pain
Eden
Penny Arcade Adventures 1 - Precipice of Darkness
Rampage
Ratchett & Clank - Quest for the Booty
Wolf of the Battlefield - Commando 3
Burnout Paradise
Championship Sprint
Fatal Inertia EX
Gran Turismo 5 Prologue
Gripshift
GTI Club+
PixelJunk Racers
Wipeout HD
Toy Home
Aqua Vita
Brain Challenge
Go! Puzzle
Elefunk
High Velocity Bowling
Loco Roco Cocoreccho!
Mesmerize
Operation Creature Feature
Piyotama
Snakeball
Super Rub'a'Dub
Tori Emaki
Trials of Topoq
Super Stardust HD
Tekken 5 Dark Ressurection
Echocrome
Geon
Linger in Shadows
Lemmings
Go! Sudoku
Pixeljunk Monsters
Puzzlequest: Revenge of the Plague Lord
QBert
Rampart
Super Puzzle Fighter II Turbo HD Remix
1942 Joint Strike
Astro Tripper
Bionic Commando Rearmed
Dark Mist
Crash Commando
Blast Factor
Nucleus
Riff: Everyday Shooter
Warhawk
Söldner-X: Himmelsstürmer
Rocketman: Axis of Evil
Feel Ski
High Stakes On The Vegas
Sky Diving
Age of Booty
fl0w
Joust
Savage Moon
--> To be continues
==PSP==
Ape Quest
Dead Head Fred
MediEvil Ressurection
Sid Meier's Pirates!
Burnout Legends
Burnout Dominator
Fired Up
Flatout
Pursuit Force
Wipeout Pure
Buzz Logic Quiz
Go! Puzzle
LocoRoco 2
Def Jam Fighht for NY: The Takeover
Guilty Gear Judgement
Brain Challenge
The Cube
Echocrome Micro
Go! Sudoku
Practical IQ
Puzzle Quest: Challenge of the Warlord
Killzone Liberation
Medal Of Honor Heroes
Medal Of Honor Heroes 2
Riff: Everyday Shooter
Super Stardust Portable
B-Boy
beats
EA Sports Fight Night Round 3
FIFA 09
Free Running
Super Pocket Tennis
NBA Live 09
Tiger Woods PGA Tour 09
fl0w
Tom Clancy's Endwar
=========US ONLY=========
===PS1===
Castlevania Chronicles
Crash Candicoot 2
===PS3===
Bejeweled 2
Cash Guns Chaos
Cuboid
===PSP===
Ape Escape
Archer Maclean'S Mercury
Castlevania: Symphony of the Night
The Con
Field Commander
Gangs of London
Gurumin: A Monstrous Adventure
Hot Shots Gold:Open Tee
Jeanne d'Arc
--------- everything after J will have to wait, I'm tired now