I've seen a lot of discussions on safety and in-mast furling main sails. The other day I was talking (more like listening) to a sailing traditionalist who was telling me how unsafe they are because if you have to take down the main suddenly and the furling mechanism gets jammed then you can't take the sail down. It's true that that's a potential hazard, although I haven't heard yet of that happening.
However, there's another side that occurred to me two days later while I was sailing from SF Bay up to Bodega Bay - an overnight trip. My sailing buddy was very sea sick and basically couldn't do anything. I needed to reef the main sail as the wind was starting to overpower the boat, and I wasn't feeling any too great either. It occurred to me that if I'd had to get out of the cockpit for any reason, or even perform any strenuous task in the cockpit, I wouldn't feel very safe doing so. Even if I'd had lazy jacks, I wouldn't have felt completely confident, especially since I've seen them get hung up and somebody had to go on deck to free them. I feel the in-mast furler was a safety factor, not simply a convenience, under those conditions.
I'm not saying I wouldn't have a boat without in-mast furling (or, maybe better yet, in-boom furling), and there are obvious advantages to neither of these systems. But it's just something else to consider about in-mast or in-boom furling.