I had a love/hate relationship with the whole process. They got the dimensions of my room wrong but refused to admit it. I emailed them about it and suddenly all of the plans were udpdated to be 2 feet narrower - in one case, a couch was situated so that part of it was now outside, in case I wasn't sure if they'd done it wrong. We lucked out because I had decided that the amount of furniture in their rendering just seemed absurd and to buy some of it and see how it went before buying more.
They don't really listen to your requests. Honestly, it was nice just to see their layouts, and then you can swap furniture in/out and reconfigure to your heart's desire. I don't think that anything that we bought (other than the faux succulents and coffee table cubes - which came in redesign 17 - yes, 17!) were selected by the folks at modsy. I do absolutely love everything in the room that I bought through modsy. It is by far my favorite room in the house. We still have to get some artwork on the walls, but it was totally worth it.
For the guest room/office, I got their cheapest package - $20? My whole goal was to find out what the largest size bed I could comfortably fit into the room and not feel cramped. DH was adamant we could get a full size bed in there, but modsy made it pretty clear that a twin XL was the best we could do.
I wouldn't recommend using modsy for small room unless it's for similar purposes. I'm not even sure I'd use it for our master bedroom. But we will eventually use it for our family room / random space that we're not sure what to do with it combo.