Yes it is as a tethered option. If you do not care about ipad2 mirroring, photo stream and iTunes match you can jb untethered but untethered does not support plex. Trade offs trade offs.
With home sharing and AirPlay from my iPhone or MBP I went untethered to have plex.
I think it is great jail broken and would not go back but that is me. Rumor is an untethered is being worked on. Go to Firecores website and check it out.