There is no right or wrong answer to any camera or system, it doesn't matter to me what anyone else uses as long as it brings them pleasure and they like the result, who cares?
I have used the Z and have run workshops with people using the Z, it does nothing for me at all but that's my personal preference, it's too big, the 2 I saw didn't work in the cold temperatures we worked in and I can honestly say that output wise, the S lost nothing against the Z in how I work. I would love the Z to blow the S out of the water because it would save me some cash but it doesn't and the S has been the cheapest camera I have bought purely because I have made more money with it than any other camera I have used, it has paid for itself many times over but like I said, it's only my opinion and it only has to work for me.
The S lenses can be bought considerably cheaper than list if prepared to look around, I also bought my first 006 body as an ex dealer demo model that looked unused for a huge amount less than advertised, add on a contax adapter and the results are amazing if you want cheaper lenses than leica own. As Pramote suggests, the options for using H, V, P67, all superb on the S if you want legacy glass.
I'm not suggesting anyone buys anything, in fact I'd rather people didn't buy the S because I'd rather be on the other side of what's popular! The Z is a great thing but makes no sense for me, if it does for others then more power to you, now go out and shoot with it!
The price for the SE is amazing, if I can I will buy another body as backup, if the 007 comes out and gives the same quality but adding extra low light capability then I will buy it because it will make me money, it's a business expense written off over 3 years and if I can't make enough to pay for it then I am in much bigger trouble than worrying about resale value.
My advice to anyone is buy what works for you and enjoy it, go for the latest tech if you want, go for what works best regardless of image/age/technology if that's what works for you and ultimately, have enough self confidence to produce the best you can with what you've got rather than spending your time questioning the choices others make when really, it means nothing.
Oh and have a nice day!
Mat
Just as an addition, I don't personally understand the pixel count thing, I have sold huge prints 1.5m wide from single S files cropped to 2x1 and they are unbelievable, lots of people have a genuine need for big prints but I would suggest many more don't, I never measure a system against mp because there is so much great software out there, great printers and the output from almost any camera is good enough to print bigger than the vast majority of normal people have space for in the houses and offices. Never once has a customer said to me, nice pic but not buying it because you used old technology to shoot it, if it had been shot with cmos or shot at 50mp rather than 37, I'd have bought it.