chaiteaso i'm going to phrase this in a way that might stir the pot a bit, but essentially it's a conceptual/fashiony thing more than functionality?
Yeah NO! The lenses available for Leica are some of the best ever made, you can choose from basically any M or LTM lens made over the the last century. For documentary work a rangefinder of any kind is significantly less intrusive than an SLR or DSLR. Also, because there is no mirror they are for the most part nearly silent.
Really though, the reason I shoot with a Leica is that over time digital cameras and lenses change considerably, it is very unlikely one will have the same camera and lens in 5 years time. With a Leica though, it is actually very likely one will still have the same lens, body, and film stock (Tri-x) in 5 years or possibly 10-20 years time. Consistency is key when working on a long term project IMHO.
Regardless, Leica haters are usually just people who either can't afford them or have a boner for AF and high frame rates.
erikKReliability, durability, artsability
Reliable yes, but zinc (M6 for example) are actually semi fragile and can be dented or damaged easily is bumped or dropped. The brass bodies (m2, m3, MP) are where durability is really a factor. Most of the really old Ms still in use today are brass. That is also what people took to war as well for the most part. As well, unlike a lot of old mass produced SLR's that just run forever without issues, Leicas will require proper maintenance by a knowledgeable technician on a decent basis. A CLA every 5-10 years if not more is a good idea, its not a bad thing to have a few hundred dollars available at all times for possible maintenance or repair.