50mm lenses are a tricky beast. See, they were nearly forgotten by the mists of history when zoom lenses came along before everybody realized they were killer inexpensive telephoto lenses when digital SLRs came along.
Now, when my daddy got me my first 35mm SLR, he followed the traditional logic and got me a 50mm lens. And I went for many many many years before I got any other lenses. And, see, my 50mm lens was made when even the cheap lenses were built robustly, so mine doesn't have the falling apart problem.
One of my friends has broken a Canon EF 50mm f/1.8 and an EF 50mm f/1.4. So clearly there's some build quality issues with the 1.4 and 1.8 lenses. So it's nice to see that Sigma realizes that there's enough of a market to make a 50mm lens that might just have good build quality...
Not sure. I have a bunch of friends with Sigma lenses who like them, but there's a lot of ranting on the Internet about them the rest of the time. I suspect this is just because Sigma's quality assurance department isn't quite as tight as Canon or Nikon's.
One must understand what it really is to understand why I say this.
Rollei took a 3.1 megapixel digital sensor (resolution 2,048 x 1536 = 3.1 megapixels) and a 2.8 prime lens. They disabled the sides of the sensor, making it a 1536 x 1536... or 2.4 megapixel image. Then they upscale this 2.4 megapixel image up to 5 megapixels (2304×2304 = 5.3 megapixels). I've already covered this.
There's a tiny 1.1 inch LCD screen where the ground glass on a non-toy would be. There's two lenses, but one of them is as real as a movie set.
And how much does this pocket wonder cost? $399! This is after Canon makes waves by reducing the cost of a good A series P&S to $180. I can see a quirky camera with real image quality costing that kind of money.
Heck, I could see a camera where they are actually HONEST about the resolution made as a fancy collector's toy be that kind of money. But doing what amounts to lying about the actual specifications of the camera? I'm sure that Rollei (or, most likely, whoever owns the license from Rollei) is going to be laughing all of the way to the bank about it.
One should also note that I've got a 50mm lens for my RB67 which is very very different from a 50mm lens on a normal 35mm SLR. Same reason why the 50mm becomes a portrait lens on a crop-factor dSLR, except in the other direction.
My earliest thought in getting something better than 35mm was to get a TLR, but even ancient Rollei TLRs are not especially cheap. Stupid collectors. The name of the game in usable old hardware is to carefully avoid any of the collector favorites.
Either way, I'm knee deep in all sorts of film in all sorts of formats at the moment.