I have no experience with the MLD products.
I do have a Hexamid solo tent though, and like it quite a bit. I find it has ample room for myself with pack inside, especially when pitched properly. I've been out in all night rain a few times and have had no problems staying dry.
No issues with condensation and it is an extremely comfortable tent to sleep in. Great views and ventilation.
I've never had blowing rain, or been out in extreme windy conditions. Did camp in snow once and it performed well.
It packs down extremely small. I wouldn't worry about longevity, as Joe has used it on his thru-hikes and if there was a problem, he'd tell you. I find him excellent to deal with and answers your questions from the perspective of a fellow hiker. If worse comes to worse you can always use duct tape while on trail. The re-enforced areas feel really solid (pole cup, tie outs etc).
This may neither be here nor there, but I've dealt with MLD and Tarptent, and no one answers my questions quite like Joe has.
The only downside is that it takes up a bit of real estate with the guylines needing some room.
I've had absolutely no problems with the mesh floor, and actually doesn't feel fragile once you see/pitch the tent in real life. However, sometimes it's nice to have a completely covered floor like you'd find in most tents with a bathtub floor.
If you do order one, get Joe to sew loops in all four corners of your tent so that you can tie up the bathtub floor to help it keep it's shape. I just ordered a cuben floor, but you can do it with a tyvek floor as well. I figure this may help to mitigate the above nitpick.
Remember to factor in the cost of a floor/groundsheet. The tyvek, fashioned into a bathtub works really well. It's a bit heavier and bulkier than the cuben floor, but it's $7 vs $100.
It only uses one trekking pole, so that you have another as a spare, just in case.
I have a door, and it works fine, but I still can't decide if the beak is better. Advantage is you can open and close the door from within, doesn't take away usable room, and you lower door for more ventilation. Ask Joe, but I don't think the beak completely covers the mesh. Though with a beak you may feel less claustrophobic and can keep your shoes outside the tent.
The Cuben Lightheart Solo looks pretty dope though, but $$$$ and I don't think you can return it. The selling point for me would be the views and small footprint (I assume). I'd also look at some of the tarptents if cost is an issue. I have a Double Rainbow for non-solo outings, and if that is any indication, tarptents seem to be no hassle, well designed products.
I find I prefer using MSR Groundhogs, or the Easton Peg stakes that came with my tarptent over the titanium shepherd hooks. Once pegged, as Eugene said, the tent is pretty solid (I've had buddies trip on my guylines a couple of times too).
Hope this helps.