I use Windows Server 2008 R2 but I don't make use of the built in roles. For example I run my own webserver not IIS and I don't use the built in FTP Server or HyperV I also don't use RDP and instead use VNC.
The reason I don't use those roles is because when there are security issues it always affects one or more of these built in roles and when it comes to updating or activating or disabling a lot of these roles it requires a system reboot. Who wants to reboot their server just to patch a security vulnerability? Not me. By using my own webserver my own ftp server my own remote GUI I can update this stuff without rebooting and keep my uptime as high as possible.
I actually have uptimes of over 100 days on my 2008 R2 server and I try to maximise that by having it as locked down as possible with minimal services and a hardware firewall making sure nothing is touching that machine from the internet that I don't allow and control.
Now about your specific questions regarding HD Media Streaming, Storage and User Accounts.
In my home we access media from our server in three ways. On our HTPC in our living room over WiFi, via our iPads/iPhones over WiFi/3G and on our Notebooks over WiFi.
With all these devices using WiFi it is important to have a strong base station with the fastest wireless specs. Simultaneous Dual Band 802.11n and of course having the Server wired to that base station over Gigabit ethernet.
But just as important is how to get the files to the devices. For Desktops/Notebooks I use simple SMB file sharing which is built in to Windows. This is the File Sharing role and I know I dogged using roles earlier but this role is internal network only and doesn't see very many updates from Microsoft. I can't actually even remember the last time it saw one in the past few years.
For our HTPC we run Plex Media Centre on the HTPC itself. Then on the server I use the Plex Media Server software. Both applications are completely free. The great thing about running Plex is that it indexes your Movies, TV Shows, Music and Pictures on the server side itself so that when you open the Plex Client on your HTPC all your media is there instantly and it is indexed correctly with plot summaries, ratings from popular critic sites and so forth. One other nice feature is when you're browsing TV Series plex actually plays the intro theme music of the show you're browsing while you're looking for an episode. It just adds to the ambience and it's a really amazing solution and again, completely free.
Now what isn't free is the Plex iPad/iPhone App. It's a single + App meaning it runs on both devices with only a single purchase. This app lets you use your device as a remote control but not just a dumb remote with virtual buttons it actually lets you browse your media on your Tablet / Phone, read the plots on the device and then you can select what you want to play on your HTPC running the Plex Client. But even more than that it also lets you play the media on your device itself so you don't even need a HTPC. And yes they do have an Android version of this app too.
Now on to storage, I'm a big big proponent of RAID, specifically RAID6. I recommend if you're going to stick 6 drives or more in to your server that you invest in a hardware RAID6 card such as an LSI 9260-8i or a Highpoint 4320. I recommend these cards because they both feature onboard XOR processors from Intel, they can both take 8 Drives and they both support RAID0/1/5 and 6.
RAID is not a backup, don't ever treat it like one but if you want a nice sizeable array go RAID6 for the peace of mind that under the event two drives were to die simultaneously your data is still retrievable.
Windows has built in capability for RAID5 but it is software RAID it is slow, it doesn't support some of the more advanced RAID features that a dedicated card does such as Online Capacity Expansion (Ability to add more drives to an already created Array without data loss or inaccessibility) and ORM or Online Raid Mitigation (Allows you to change from one RAID mode to another without data loss or inaccessibility).
User Account wise, I personally like to just create 2 accounts. The main root account which is where I'll administrate the server and then a locked down user account which is what will share my storage through file sharing to my home network, run my FTP server and so forth.
I hope some of this was helpful!
). And offcourse the raid-card just gonna order one that you advice me. And I'm not using wifi at the moment because everything is wired up. And I'm waiting for the nu asus transformers to come out, so no tablets yet
