WSUS is OK... for a free product, it does what it says on the tin. There are much better applications out there, but unless you're prepared to spend some money then it's an acceptable solution. I don't like the way that Microsoft went from WSUS 2 being web-based to WSUS 3 being an MMC snap-in, but that's just personal preference. Oh, and the built-in reporting sucks... we write our own reports instead.
Are you planning on using SQL Server or just MSDE? If you were thinking of using SQL Server, were you planning on installing it locally or remotely? If it's local, then factor this into your disk requirement. Also, think about backing up your database - are you going to store the backups locally (and then backup the server) or just store the database backups remotely? Again, if local, then factor this in too.
Even just for the WSUSContent directory I'd say you'll run out of space very quickly, as others have already pointed out.
Are you planning on using SQL Server or just MSDE? If you were thinking of using SQL Server, were you planning on installing it locally or remotely? If it's local, then factor this into your disk requirement. Also, think about backing up your database - are you going to store the backups locally (and then backup the server) or just store the database backups remotely? Again, if local, then factor this in too.
Even just for the WSUSContent directory I'd say you'll run out of space very quickly, as others have already pointed out.