I've been running an HTPC of some kind or another for almost ten years now, and my user interface has finally come (almost) full circle.
In the very beginning I had a Windows laptop attached to a television and the user interface was the Windows 98 Explorer. There was no skinning, no scraping and no metadata database. I browsed filenames, double clicked them, and they played.
Then, starting in the fall of 2003, I began using XBMP and then migrated to XBMC - both on the original XBOX hardware. This was attractive because the XBOX was an instant on/off device with a television-ready video output (unlike a PC). (In fact, I would say that XBMC, on an XBOX, right after the spring of 2004 when DVD ISO support was added, was the high water mark of the HTPC. It played everything, there was no on-demand ecosystem (like Netflix) to take part in, and there was almost no high bitrate content that the XBOX CPU could not handle).
Unfortunately, this sweet spot only lasted for about 6-12 months. Every day more and more "high definition" content was extant, and the XBOX did not have the CPU horsepower to play it.
The next step for me (after procrastinating for a year or so) was a mac mini based HTPC which required some form of "HTPC software" - not because I wanted such an interface, but because of the codec landscape, which Quicktime was ill equipped to deal with. If you wanted to play the file formats that you would find in the wild, you needed something more than Quicktime.
So I moved to "HTPC Software" because I needed the codecs, and ended up following the entire arc of OSXBMC and Plex and later returned to the mainline XBMC on OSX.
Through it all though, I never set up any scraping, never installed any plug-ins, and metadata caching (especially of tens of thousands of mp3 files accessed over a network) never did anything but paralyze my system. In fact, all I ever did, from XBMP on the XBOX to Plex on the Mac Mini, was choose filenames and play them.
And so with a recent OS reload on my Mac Mini HTPC, I skipped that software layer entirely. I use the Finder to choose files, and they play in QuickTime Pro with the Perian components. For DVD ISOs, I simply double-click them and after they have mounted, start the built-in OSX DVD Player application.
Finally, for live, or on-demand content, I just use Safari.
So, instead of a Netflix plug-in, like one uses with Plex:
I just use my web browser (Safari):
The only downside so far is that I have a fair number of MPEG Transport Stream (.ts) files that are not handled by Quicktime in any way, regardless of plug-ins. I can live with this, as they usually had playback glitches in XBMC/OSXBMC/Plex anyway. I'll just convert them to MPEG-2.
The Spaces virtual desktop interface in OSX makes this work very well - I simply run a full screen Finder window in one space, and a full screen Safari window in another, and have configured the two side buttons (the "squeeze" gesture) on the mouse to engage Spaces.
Other than Perian, no non-default applications need to be added to my OSX HTPC. This is very appealing to me, and more then makes up for the loss of a "sophisticated" user interface. In fact, it is Perian that makes all of this possible, as the default codec support in Quicktime is not sufficient by any means, and it is important to note that this "back to basics" HTPC will only work so long as Perian keeps up with the current codec landscape. It is for this reason that I encourage you to donate to their project.