They can work, but IMHO, have about zero style. One piece bits first need the floor to be perfectly level, which is possible, but unlikely. There are ways to make that work, primarily by setting the pan in piles of mortar to level it and help support the bottom so it doesn't flex. If it isn't, your drainage won't work well, and the walls may not fit, or leave uneven gaps, or the floor flex creating stress fractures over time. That also means the corners must be square and the walls plumb. On most, there's almost no leeway on where the drain is...it needs to be nearly perfect, and that may need to be moved if you can't move the whole shower slightly to accommodate it. The drain often seems to be just up against a joist, making that a major issue. Sometimes, you're lucky!
THere are situations where that may be the best choice, but I'd prefer a tiled shower. IF that's a consideration, check out
www.johnbridge.com where they specialize in things tiled and showers is a big portion...tiled or not.
