A Boring Dystopia

There's an Apple data center near me. They feed the hot water into the district heating system and use wind for electricity.

Even if it's environmentally neutral, it's still a ressource hog. Other businesses who want to switch to electricity are currently put on hold, because the data centers are maxing out the grid capacity. I guess it's a luxury problem, but they're causing delays for other businesses in going green, and all only for the purpose of storing iPhone messages and family pictures.

They have about a dozen employees. I think it's mainly security. This has received some criticism because they originally pitched the idea with thousands of new jobs.

So overall, even in a best case scenario it's waste of renewable energy and area which doesn't create any income.

The heat you have available in a data center is pretty low-quality (cold) heat. If you're not familiar with the field, a (very) basic introduction is looking at the Carnot efficiency: In principle, you could increase the pressure in the water with a pump, then let it evaporate, before extracting work in a turbine. Then, you condense the steam (by heat-exchanging with the ambient) before sending it back into the pump.

Now, if this process is ideal (frictionless pumps and turbines, perfect heat exchangers, etc.) we can figure out how much of the heat energy that can be converted to useful work (turbine output - pump input). Assuming the ambient (our cold side) is about 25 C, and the racks we're cooling (our hot side) operate at around 100 C, we get a Carnot efficiency of about 0.2. That means only 20 % of the heat can actually be converted work. Again, this is the ideal case. It is not thermodynamically possible to get better than this. Realistically, you could maybe get 10 % or something.

So, bottom line: The racks aren't really hot enough to extract meaningful work. A better proposal would probably be to build things like this in places that are cold and require heating, so that you could use the waste heat as a district heating source. In that case, you could more or less completely eliminate the need for other heating sources in homes (which are far too often electrical). Then, we would be using the electrical power (which is high-quality) for something "useful" (disregarding whether or not a data center is useful in the first place), and use the low-quality heat for what it does best (heating things to moderate temperatures).

It's unfortunately just warm water, not steam, so it's pretty hard to extract energy into it in any meaningful way

If you put a turbine in the cooling tower, it'll take energy from the water by slowing it down. This will increase the humidity at the bottom of the tower, which impedes the liquid water from evaporating. This makes the tower cool slower.