It doesn't seem all that long ago when spending 3 times the price of a Raspberry Pi on a 512MB hard disk would have seemed like a bargain for a decent amount of hard disk storage (and I'm talking about 'real' money'!).
I'm thinking of using one to make a streaming media player using XBMC or similar. Only _thinking_ about it, mind you! :-)
I don't think the 512MB ram limit will be an issue for this sort of task. A 1GB limit would have been a more emotively satisfying limit (rather like the 'stand out' feature of a microprocessor that could address a whole 1MB of ram in a desktop computer, the IBM PC, as opposed to all of its contemporaries which were limited to a poxy 32 or 64 kB without resorting to bank switching).