I'm not sure why you need to run it in a chroot but I tried without it and couldn't get it to work. It's not a hardship to run it in a chroot, it doesn't take more resources, just space.
I left it to import the library last night and it's working very well this morning. Scrolling through the media is smooth and responsive. Fast forwarding to midway through a film is quick. I don't have any media that needs transcoding so I can't test that, but I can watch everything on my mobile.
I'm running it off a 8Gb MicroSD card, I might do it again with a 16Gb card as its already 83%, half of which is the meta-data from the library.
I think my setup is slightly different to amok's. I'm running it headless with just the network and USB drive cables in the rPi. I use the plex app on my phone/PC to watch or cast the media to a Chromecast.