I think he's boom or bust but for athletic/size reasons mostly. Maybe MLF can actually use a little guy.

As a player in general, he mixes up his speeds well and is a pretty good route runner coming out of college. Knows how to get separation and has quickness to do it. MSU WRs have to block to get on the field so he's not afraid to do that either.
He is very undersized for what GB likes but it's easier to be cat quick at 5'11 vs. 6'2". He's shifty but not smooth if that makes sense. His contested catch/jump ball ability is surprisingly good given his size. If you watch some of his games he's going against CBs taken around or before he was (Joey Porter Jr., Ty Stevenson, Quan Martin, etc.) and can hold his own. I think he's a smart player, there were times he adjusted well in the scramble drill or adjusted his routes to coverage.

Some thought he was the best PR in the class, not sure I agree but he can help there too which matters.

Seems like his speed is good enough, often was able to increase or maintain distance from chasing players on big plays. Had something like 46 plays of 20 yards or more in his career, so he can be a playmaker.
One last thing: seems like he's got some toughness or dog in him which I like. I think if he's a feisty slot guy with good quicks and speed he'll be a good compliment to what they have.

Would have liked him in R3 but I thought Kraft was good 'value' in R3 so you could basically flipflop them and call it a good set of picks.