Play, yea if the joints are really tossed you may feel it. The other consideration is how tight the thing is, as in when you move the knuckle around are you feeling the spring. It should not flop around easily, if it does scrap it. The other major thing to know is if it aftermarket full spline or not.
From what ive seen, the aftermarket ones have greasable joints and center ball. The ones from a cadillac are not, sure you could get it re-built with greasable joints.IIRC the rebuild kit was about $90 when i had mine done.
Durability is another factor, i had a full greasable full spline i bought off of CL it was nice and tight with plenty of spring action, The POS came the F**K apart after about 1500 miles(all pavement at the time). I Took my ass out to pick n pull found a caddy ,pulled the driveshaft and munched the end at the diff with torque converter.$30 later for a damaged part i had it set to the proper length.5k miles later not a problem to report .
Material for a standard driveshaft is$30-$40 and an hour labor at a driveshaft shop(was $65/hr)