I've got a copy of Diesel Power somewhere from a year or two past that had an article on several of the GTL and BTL processes.
As far as the natural gas to liquid process, most often what they refer to when talking about GTL, this is one the oil companies like - it actually saves them money and gives them more product to sell.
Instead of having to build natural gas handling facilities and pipelines, or shipping it as CNG or LNG, or simply just burning it off in well head flares, it allows them to convert it into an easily transportable form (distillate fuel) that's in just as much demand as natural gas.
From what I've read, these GTL processors can be made small enough to be somewhat mobile - this allows them to transport these plants out to smaller natural gas fields that wouldn't be worth the expense of recovering by conventional means, convert what gas is recoverable to liquid distillate fuel, and simply ship it out via tanker truck or a conventional pipeline.
If I remember correctly, in the same article I mentioned the country of Dubai was building a large GTL plant - they have large natural gas reserves but no easy/economical means of storing and transporting it to other countries. Instead of simply burning it off at the well head, they can now convert it to an easily storeable and transportable form.
It also stated in the article that besides being much cleaner than regular ULSD, the fuel created by the process came out at 73 cetane!

Can you say rocket fuel? That would be one other reason for blending it with ULSD - cuts the GTL down to an acceptable cetane level, and a nice cetane boost for ULSD.
One gent at work some years ago spent some time working in the oil fields in Alaska. He said at times there was so much heat generated from the well head flares burning off natural gas that you could literally work outside in your shirt sleeves in the middle of winter. Talk about CO2 emissions and a colossal waste of energy - imagine if that natural gas could be converted to liquid form such that it could be transported in the existing pipeline or at least via tanker truck to market.