This is to add to user30007's answer. I will write more later, but there are important points to add to this discussion, more than can be put into a comment.
First, I've run across several articles that came up high on the list from a Google search that are full of errors. At the bottom of this post I'll give a couple of examples.
Titan's surface temperature is roughly 94 K, ~-179 C, but it increases with depth below the surface. There is considerable disagreement about the thickness of the ice crust: some say as little as 50 km, as mentioned in the question, but others say as much as 200 km. Whatever that thickness is, the temperature at the ice/ocean interface is below the 273.2 K "normal freezing temperature" of pure water due to dissolved salts and/or ammonia (briefly summarized here). But due to the normal subsurface thermal gradient the temperature at the bottom of the ice crust is well above 94 K.
In the comments there are suggestions that bound on terraforming Titan, including "planting trees". There is a big problem with that.
Here on Earth, the crust is fairly strong rock, with the bulk of that rock composed of minerals like quartz, and feldspars such as plagioclase and orthoclase. Those minerals are strong solids at the temperature range of Earth's surface. Water can be a liquid, a gas, or a weak solid — but not on Titan!
Everywhere on Titan's surface, and for many km below the surface, water is very much like quartz is on Earth: a strong solid. Titan's crust is mostly solidly frozen water! (From Cassini and Huygens measurements the "soil" appears to be mostly organics, not metal oxides)
If you bring Titan's surface temperature to a level compatible with growing trees, the entire crust melts! Sure, that would take a while, but it would be from the top down. With time, the now-surface-water ocean gets deeper and deeper, until the entire crust melts. Everything denser than water would then sink to the surface of the high-pressure ice shell (Ice-VI?) that surrounds the silicate/metal core, some 400 km down. The silicate/metal core is another ~100 km down.
If you bring the surface temperature to something colder than that but much warmer than the current temperature, eventually (millions of years later?) the bottom of the crust warms and melts, thinning the shell and making it more unstable under the various stress fields imposed on it, like tidal stresses, viscous stresses from sub-ice ocean circulation (if there is any), etc.
As a site for human occupation, Titan won't have a "shirt-sleeve" environment for a long time. The amount of energy it would take to warm Titan to that extent, and keep it warm at 10 AU, is truly huge, beyond our technological capabilities for the foreseeable future. And if we ever achieve that, human habitats would be on floating facilities.
Now for examples of erroneous material out there in web-space. For instance, this NASA site says that "...the atmosphere extends to an altitude 10 times higher than Earth's—nearly 370 miles (600 kilometers) into space." This makes it sound like it would be safe to orbit at any altitude higher than 600 km. When I was working Cassini operations, deciding how low we could go during Titan flybys, the then-current atmosphere models suggested we could go as low as ~950 km altitude. But when we actually flew the spacecraft just below 1000 km, the atmospheric drag forces were high enough that we nearly lost attitude control! The atmosphere goes well beyond 600 km. That same paragraph says that the pressure at Titan's surface is "...roughly the same pressure a person would feel swimming about 50 feet (15 meters) below the surface in the ocean on Earth." That would be true if the pressure at the ocean's surface were zero, which it is not — it's one bar, so the pressure at 15 meters down would be 2.5 bars, not 1.5. This article was probably written by someone on NASA's public affairs staff and not checked with an appropriate scientist. I wouldn't trust anything in it without verifying elsewhere.
Surprisingly, a Wikipedia article about Titan's climate sports a glaring math error that carries into the up-front Google search result. It says Titan's average surface temperature is 98.29 K and then says that is equal to -179 C. -179 C ≠ 98.29 K ! -179.00 C (which is close to correct) is 94.15 K. A general summary of Titan temperatures is available in the abstract of this paper by the Cassini CIRS team, and the full text goes into much more detail.