I wouldn't say it'd be good directly before a workout… it's like chugging a big glass of water! You might get a little sick too close to working out.
I just drink it in the morning, have a bit of food, and it works out well. It provides me, mainly, stuff that I don't get in my diet, and helps me fill in the deficit of Iron. I really notice when I don't drink it, I get very tired all day. I don't really think of it as a "meal replacement," more like a diet enhancer for me 😛
The increase in energy and stamina and stuff is more overall- I don't get a burst like I would with caffeine.