It's interesting hearing the different experiences.
I added a 3-Eleven to the garage earlier this year, as I wanted something a bit "more" than the Elise Cup. I've been absolutely thrilled with the car.
On the track, it's definitely a handful in comparison. I find the Elise very flattering on the track. A few laps & I'm normally pretty comfortable. If I make a small mistake, no big deal as the Elise deals with that pretty well. Not quite the same in the 3-Eleven. Of course, everything is coming at you a whole lot faster, but it also requires you to really stay in tune with it & have a better awareness of what's going on. I feel like I always have to be feeling the car & adjusting appropriately. If I go just a hair past my breaking point, it makes a bigger difference than the same mistake in the Elise. On the other hand, when I start to absolutely nail a turn well, I find that I'm now needing to adjust more and more for the next turn as my speed, at what was my breaking point last lap, is now much higher. Of course, some of this likely comes down to me being a rather middling driver, and probably perfectly normal for a better driver, but, brutal speed & acceleration aside, it's definitely been the biggest difference between the two cars. I actually really like this aspect of the car though. I've had occasional points with the Elise where I just feel like I'm going through the motions while turning a lap. The level of involvement when driving the 3-Eleven means I've never had that, expect for perhaps during a cool-down lap.
On the road for a nice Sunday drive through the local hills I find I enjoy the 3-Eleven more than the Elise at non-license losing speeds. Much more visceral, even at low speeds. The wind, the occasional dips & rises in temperature, the smells, the sounds... the everything. It's all there & amplified. The Elise would still win out for a weekend getaway with the wife, but just a nice morning of alone time... 3-Eleven any day.
Regarding comfort... definitely decent eye protection when driving around town or at reasonable speeds through the local hills. Autobahn excursions (I drive to/from the track as well), mean I'll be wearing my helmet. Some debris getting kicked up when you're in a normal car may mean a cracked windshield. I don't want to find out what that might mean when your face is the windshield. Unlike others, I have not found the outside temperature to really be much of a bother. I'm on the shorter side though, so I'm pretty well tucked into the cockpit. I can't say I've ever felt any real wind on my hands & once the car is warmed up, the heat coming up from the radiator just outside the cockpit is actually quite noticeable (big negative when sitting in traffic in mid summer). Above ~200 or 220kph on the Autobahn & wind buffeting on my helmet gets to be pretty bad. No helmet lift problems for me (again, I'm sitting pretty low in the cockpit), but my helmet can shake around quite a bit. Adding the spoiler & chin aero bits to my Arai helmet has helped somewhat, but I'm still want to find something better.
I try to avoid any sign of wet, but the tonneau cover + some basic rain gear have getting caught in the rain not all that bad. If it wasn't for a bit of traffic, the rain gear probably wouldn't have even made a difference. Once you stop moving though, the rain is going to fall on you, so a nice set of waterproofs comes along anytime I'm headed to the track & there's a chance of rain in one direction or the other. I still have the Elise, so if it's more than just a chance of rain while on the way to/from, or if there's a real chance of rain during track time, I'll drive that instead. Largely though, neither car gets driven in the rain.
Truly my biggest complaint about the entire care would be the windscreen on the tonneau cover. The top edge of it cuts directly across my line of sight & so I've just simply taken it off for now (again, I'm relatively short. I'd bet if your 5'10" or above, it wouldn't be an issue). Getting a spare & cutting it down just a hair is definitely on my to-do list for this next year. Windscreen on the 2-seater cover doesn't quite have the same effect as it's not transparent & so just cuts a small bit off the bottom of my vision, which would only be seeing the nose of the car anyway.
It's a great car & tons of fun. Sad that there's not very many of them out there, but there were many more 3-Elevens at track days this year than I saw last year. (I'm guessing way less than 311 cars were built. I think the count was 103 Road cars before the start of production on the 430 model, and there were only supposed to be like 20 of those... so 188 Race cars were made?)