Because you have Uggla, I'd totally do it.
If it helps, I just dropped Snider to get Jennings. I can afford to try him out as I am playing the last place guy this coming week and I have a fairly large size lead going into today.
Upton becomes trade fodder with the promotion of Jennings, and while I am giving up more power with Snider, I am gaining 4 tools out of 5 with Jennings. And Jennings does have some pop based on his AAA stats, so definitely take a chance before someone else does.