I just started using Soylent a couple of weeks ago and so far I've lost ~10 lbs.
I've mostly been trying to eat only Soylent, though I've had many days where I've eaten other food in addition to Soylent. I typically have Soylent once a day, if not for all three meals a day. Rarely have I had a day where I only eat Soylent, but I try to as often as I can. I just give into my cravings or a bagel or sandwich too often
I typically shoot for three meals of Soylent a day, which equates to 1500 calories. At dinner I'm often a bit hungry, so I'll have some ramen (360 cals). Or in the afternoon at work I'll be hungry, so I'll have some beef jerky as a snack (90 cals per serving). I try as hard as I can to stay under 2000 calories a day, and if I get close to that or go over, I try to offset it by walking a lot or riding my bike.
I use a Fitbit to track my steps and use Runkeeper to track my bike rides.
So far I'm really happy with the results and want to push harder over the coming weeks. I've got a month's worth of Soylent now and I hope to get as close to my goal of losing 30 lbs (over several months) as I can.