I've heard NZBGeek.info is pretty good and worth the lifetime fee (currently $30) as far as indexers go. I've also heard that free software like NZBGet which takes in the NZB's and downloads everything for you, verifies the download, and does the unpacking automatically, is great and has its own browser interface. I've also heard services like newshosting.com are worth the $15 unlimited bandwidth access given their speed and retention.

I'm told these are better than torrent primarily for speed and accessibility. Accessibility is key for older content as these massive data centers that belong to the usenet provider will typically hold all data for at least 7-8 years. So if you are within the 7-8 window you won't have any speed or "seed" issues. The issue now for Usenet seems to be DMCA takedowns which applies to new, popular content. Although, if one were to use software like SickBeard or SABnzbd, I've heard they automate the locating and downloading of recurring/episodic television and would replace NZBGet. You set your preferences for a show (quality, language, etc.) and it does the rest because it knows when the show airs so you literally just find new commercial and add free TV downloaded and ready to go.

Combine this with Plex and you're golden. And that's a $30 one time fee and $15 monthly recurring in total, as the rest is all free software. Unless you want the premium Plex which you would only need if you want to stream from your home to your mobile device or something else while in transit. But if you just want to use this to watch at home, then Plex is also free, fantastic software...or so I've been told.

EDIT:

One additional note on legal protection - using Usenet is preferred as you are communicating directly with your service provider (i.e. newshosting.com) for them serving you files. This means there's no one monitoring the swarm and trying to see if you are seeding or serving/distributing the data. So there isn't going to be anyone serving you violation notices or suing you for illegal distribution. Another benefit is those Usenet providers are typically on major internet backbones and typically max your line speed even for extended usage. You can easily pull down several hundred mbps constant for most Usenet providers.