Hi AC,
...actually, I've seen some that didn't look half-bad, were reasonably integrated to the lines of the boat... Invariably, they were center cockpit designs, it's very difficult to make an enclosure on an aft cockpit boat appear to be anything other than an afterthought, a boxy add-on...
But, IMHO, it is difficult to overstate how inhibiting a full enclosure can be to actually sailing most boats... Even a simple operation like docking can be a real problem... The Tayana 42 I delivered south this winter, I really don't see how it would have been possible to put that boat in a slip, and secure the stern lines to a pair of outboard pilings. Even something as simple as adjusting the windvane was a nearly impossible chore on that boat, the enclosure was so restrictive...
And, until you've sailed at night, or in the fog, from inside one of those things, you cannot believe how greatly they can restrict your vision... Even the slightest amount of lighting from compass or instruments is reflected on every panel, greatly restricting your vision of anything beyond... I couldn't believe how much more difficult the simple act of standing watch offshore, and routinely scanning the horizon, is made from inside one of those freakin' things... Trying to enter a port or inlet at night, in dirty weather, everything around you being doused with spray, it's a recipe for disaster...
I believe strongly that sailors make a big mistake in trying to isolate themselves from the elements, to the extent that many of these enclosures attempt to accomplish... That 45' Hardin that was abandoned a few years ago on the way to Bermuda - with the loss of the skipper and another crewmember - one of the surviving crewmembers stated afterwards that the full enclosure contributed to the event, in that they were not as aware of the deteriorating conditions as soon as they otherwise would have been had they not been inside such a cocoon... I've had that same experience several times myself, too much "protection" from the weather can really desensitize you to changing conditions...
For motoring down the ICW on a chilly day in November, when you're gonna be tucked into an anchorage or marina before nightfall, sure - they can be the cat's meow... But for anything beyond that, they're certainly not all they're cracked up to be, and in many situations, can really be an impedance to safe navigation, the simple pleasure of sailing, and safe movement about your boat...
Just one gasbag's opinion, of course... (grin)
best regards,
Jon