Very Slow! If you've been playing COD4 a lot, you'll feel like falling asleep. Just remember, this is a tactical game. It's more about position and precision.
It's also not a casual game by any means. As some have already mentioned, the controls are vast. Some would say it's unnecessarily complex. For example, there's three different ways to target people. The default setting is auto aim. You go up to someone, press L1 to target, R1 to shoot. The auto-aim distance is really small for everything except SMGs. If you press square at any time, auto aim shuts off and you can over-the-shoulder aim ala Uncharted/RE4. Finally you can enter FPS mode by holding L1 and then just pressing triangle. There's advantages and disadvantages to each mode depending on gun and depending on your position. It's a lot to keep track of but personally, climbing the learning curve is really satisfying.
One thing that I think is cool is the points system. Different style kills are worth different point values. Headshots are worth more than killing someone with body shots for example. Goes to show the emphasis on precision. To kill someone with autoaim, you often have to unload an entire clip. So it can be to your advantage to take some shots to lineup a headshot.
There's more I could talk about, but I'm tired. Overall, I'd give the game a B or an 80/100. I'm not too thrilled about the 2 maps (Grosnygrad is okay, but Bloodbath is just uninteresting and too small). I think the CQC melee moves need to be more responsive; it feels like there's a slight delay between the moment you press the button and the moment you execute the move (at least when CQCing with your primary weapon). I also think the speed of the characters should a bit higher. If they make some improvements, I'll probably buy the full MGO game. Otherwise, I might just stick COD4 and perhaps GTA4 multiplayer.
My Top 5:
Shadow of the Colossus, Metal Gear Solid 3, Shenmue, Skies of Arcadia, Chrono Trigger
My 2 nex-gen systems: PS3 and Wii
Prediction Aug '08: We see the PSP2 released fall '09. Graphically, it's basically the same as the current system. UMD drive ditched and replaced by 4-8gb on board flash memory. Other upgrades: 2nd analog nub, touchscreen, blutooth, motion sensor. Design: Flip-style or slider. Size: Think Iphone. Cost: $199. Will be profitable on day 1.