I have a wallet and a purse and I've never had a problem with either. The lighter straps (like on the classics) darken over time just from your natural oils. And I don't think that putting any leather bag in the rain is a good idea.. You just have to take proper care of them :)
If you get the classic monogramed bag the handles do oxidize and become a caramel color but that is with any good quality leather bag. if that is what you are worried about then get a bag with darker handles that you can't see the color change.
Of course it's leather. But that shouldn't stop you from buying a LV bag if you want one. With any purse wether its high end or not you should take care of it. Of course higher end purses need a little more care.
The handles are normally untreated leather so they are easy to leave marks on, if wanted you could get it professionally treated so you don't have that problem. The purse itself does not have that problem and like any good quality leather it does get worn into but I personally like that better!
I actually much prefer them when they look more worn in...especially the handle. The regular wear and tear of leather bag should be expected. It can withstand rain but would I be worried if I spilled a glass of water in it? Absolutely. Just use your best judgement.
These bags are made of the highest quality leather and with all leather you have to treat it right! no leather should be exposed to rain and wet. the leather naturally ages, oxidizes and becomes darker but doesn't ruin.