A 1TB hard drive will cost you about $60, and it should last for 5+ years. SSDs have lower latency, are silent, and suitable for the professional who has more cash to burn.
The main reason I can't imagine running off a non-SSD anymore is that these laptops are also old.
For me, spending some extra cash on an SSD for my X60 was actually a money saver because it made my X60 lightning fast and killed any immediate need for a new machine. I would avoid my T61 with the non-SSD a lot of the time because, even though they had otherwise similar specs, it'd be ~5min to logged in session versus 30 seconds, and everything else just felt so painful and slow... The SSD was the single biggest boost to performance I've ever made, and made me quite content to continue using these old 2007 machines.
A local file server is essential if you intend to keep backups, whereas a local cloud server is more helpful if you're setting up a media library for family members etc.
My living room computer is kinda of all of the above... it receives backups via rsync/ssh, I can connect to it via SFTP (locally or remotely) as a file server, but it's also running ownCloud (and a few other web applications). I'm somewhat tempted to make that my home base... just access it via SFTP when I need to get into long-term storage files or something, maybe even just stream my music collection... but I'm really not sure yet!
Thanks for the feedback. :)