Woo. Finally something I can help in!
1. You can save files (music, pictures, videos) via the wi-fi from your media server or with a hard connection. Same thing. You'll need to setup the media server on your pc via Windows Media or another program. I'm running Tversity. (Free download at
www.tversity.com). Windows media is not able to stream xVid files, so Tversity is probably the better bet.
1a. You cannot access the PS3 from your computer, but you can access media files on your compter from the PS3.
2. The PS3 should be able to play music and pictures at the same time. I haven't done this before, but try playing a music file, hitting the PS Button and navigating through the picture menu.
3. In regards to using the PS3 as a music source, it's definitely viable. However, I prefer streaming the files over my wireless network. This way, I don't have to waste the space on the harddrive of the PS3. I have 300GBs of storage on my PC and an external 1TB harddrive. The other reason is that I don't want to duplicate my music/video files - it'd be a hassle to have to copy it all over when u can remotely access it all anyways.
One function I have become absolutely infatuated with on the PS3 is how it links to the PSP handheld system. The single coolest feature I have seen in a long time is called Remote Play.
Basically, using a PSP, you can link wirelessly via internet or homenetwork to remotely turn on your PS3. From there, your PSP will act like the screen for your PS3. You can do just about anything you can do on the PS3 on the PSP at that stage except play PS2/mostPS3 games, watch DVDs or BDs.
However you will have access to your video, music, pictures and PS3 browser. If you have your PS3 connected to your media server, you can also access that as well.
Ever since Sony added this feature in the 2.10 update, I always keep my PSP in my car. If I'm at a coffee shop, I'll bring it with me and connect to their wireless hotspot, and watch a movie or listen to music or show friends my photos from my computer at home. Definitely very, very cool. In fact, that see this as the next new wave of technology - no need for tons of storage on a portable device if you can retreive your files from home anywhere, anytime.
Oh, another thing is that you can play any PS1 game via remote play as well. There's a bit of input lag, but it's still pretty neat.
Just think of the PS3 as a media conduit - it does pretty much everything - including playing games.
If you want more PC-like functionality from it, you can install Linux, and it will be just like a computer in your theater room.
Apparently, they're trying to add PVR-like functionality to the system in the future so that you can record TV, but I haven't heard any news on that lately.
Oh - and games. Get a good game or two. You'll be amazed at how far games have come since the Pong days.