DVDs or on-demand movies? Some pundits would have you believe it's one or the other, but you can walk the line and enjoy both. All you need is a Blu-ray player that has apps.
Like this one: While supplies last, Quick Ship Electronics has the refurbished Sony BDP-BX58 Blu-ray player for $64.99 shipped. It's without question the most loaded set-top box I've seen at this price.