Some of what you are asking depends on preference more than anything.
First question is how much data do you want to keep? Not that I would recommend this at all, but on the low end of things, if you intended to keep only the last backup, you would only need only one folder because it would be simple to keep track of, and that would get overwritten daily. Obviously most companies want multiple copies so they have redundancy, and the ability to go back in time. The question becomes do you want to store it all in one folder or not?
Multiple backups can be stored in the same folder, and when you run the wizard, it actually defaults to keep 100. Restoring any of these is not really difficult since BE keeps pretty good track of when the backups were created. So if you went with this, you would not really have any problems.
That said, you could certainly create additional folders, which each show up as a different device. You could make one for each day of the week, a weekly backup, a monthly backup, or even yearly backup, depending on how much storage you have available for posterity. This requires a little more in the way of setup, and is akin to an autoloader, and I would personally have a preference to this since I like autoloaders.
Normally, I would overwrite the daily backups, so Monday would overwrite the last Monday, but I usually keep the last 4 Saturdays, then a monthly backup. Some companies certainly might keep more data if they have the storage.
As far as restoring, this is the same as tape. Although the restore resources have slightly different icons than a tape, you can restore a single file, database, or even mail item (if you are using GRT), just as you could with tape.
I suggest that you create a Backup-to-Disk folder and run a small test backup of some static data files, your Exchange, a few small SQL databases, and the system state. After that, look at the directory structure in the folder to get a feel for what it looks like. Then, although you don't have to actually run it, check out what the resources look like if you were to attempt a restore. That should tell you all you need to know.
