I saw it last night from the rear row on the first level and thought it was very effective immersive staging. If you're at the tables, particularly at the front end by the counter (and especially the center table), you'll definitely get up close and personal with the performers.
It's a small, intimate space and the three piece orchestra sounded fine, although it was my first time seeing a production, so I have no comparison. The performers are miked but not over amplified.
I'd still like to see the second half of the run, but glad I got a ticket to see the UK cast when it popped up a few days ago. Jeremy Secomb kept a good poker face, which made the depth of emotion pop when a smile crept in or his eyes twinkled - or he bellowed out in rage. Siobhan McCarthy was the perfect match as Mrs. Lovett, and "A Little Priest" got a rousing response. I also thought Joseph Taylor was endearing as Tobias.
Re: earlier questions, they have a windowcard ($20) plus t-shirts, a mug, and magnets. They seat you through the door that is by the pie counter, but for intermission (without spoiling it, I loved how they started up again) and after the show, the other door behind the rear seats also opens.