Vudu is an excellent service for a number of reasons. They absolutely run on anything for one. They're 100% platform agnostic and Wal-Mart doesn't own a tech platform, so they're not favoring any given streaming player or operating system over any other, and nobody's got any reason to block them or play games with them, unlike if you buy from Apple, Microsoft, Google, Amazon, etc.
Most of the creative new ways to getting your digital copies started with them like Disc to Digital and Instawatch. Others have dabbled in it, but Vudu really made these things happen and they've continued to be the biggest in these spaces, though Best Buy has recently dabbled with giving out digital codes for preorders in advance of physical releases.
And on the front of digital ownership, they've continued to support issuing UltraViolet rights on every single title they're allowed to do so by the studios, and seem to plan to continue to until the last possible moment (Whereas Fandango voluntarily dropped it for all MA-eligible titles pretty quickly) and were immediate to grab into Movies Anywhere as well. Most digital copy codes for titles that aren't UV or MA are also redeemable on Vudu.
In the buying digital video space, they've really stood out as the safest best to ensure your purchase or digital copy will be available on any device more or less in perpetuity, and that makes them my default for it in the world where video still hasn't won good DRM-free options like music and ebooks have started to.