$40 for a complete system is a great deal, I paid about that much for mine. Oddly enough I just did a video review of the PCjr asking that very question of is it worth it: vid at youtube.com/user/phreakindee
Short answer: no.
Long answer: no, unless you're interested in those things that make it unique (cartridges, historical value, a few specific games or apps, IR keyboard, the cool look)
If you have a Tandy 1000 you're not going to get much you haven't already seen software-wise, and the Tandy will likely do a lot more anyways, for games especially. Compatibility with some PC and CGA software exists but it's not as bad as some make it.
The video goes into much more detail, but again for $40 for a whole system heck yeah.