Rain isn't an issue, plan your camp as usual on high ground, snow just camp right on top of it like a normal tent (a tent floor is not good insulation). This will be my first year but plenty of guys that use these have been in downpours with no water issues, i'll put a piece of tyvek under my pad. Also if cold enough pack a stove and it will dry stuff out quick.
Oh yeah, if you take the stove add 1.5 - 2.5lbs to shelter weight depending on brand.
I don't pack a ground cloth, but a few of my friends bring a sheet of Tyvek (weighs 4 oz's) for a ground cloth when using a tarp.
I just posted a video from my solo backpacking trip and on Saturday night it rained for several hours. I pitched my Supertarp on a bench at 11,500 feet and the rain only came in about 2 inches under the edge. I haven't had any issue with water coming in any farther than that and I've logged many nights under the SUpertarp.
A mountain hardwear drifter 3 most days. Not the lightest but it provides a lot of space for the weight. I have a GoLite Shangri-La 5 with stove and stove jack for the colder nights in late fall. I might take it as a spike camp cook tent/warming tent for the elk hunt this September. We have three guys going so taking 3 tents isn't too bad. Two domes for sleeping (Dad and I in one and cousin in another) plus the GoLite for shelter from rain or eating in at night with the stove going.