Quite true that composted manure is 'compost'. It may be a bit higher in nitrogen than other composts, but once composted, it won't 'burn' plants so you can use about as much as you want. It may be a bit higher in salts but only an issue if you live in a very dry climate where salt accumulation is a problem. I do like to mix different composts if I'm having to buy them. They all have a bit different ingredients and the resulting nutrient ratios are different.
One clarification I'd like to offer on the earlier post about ammonia 'bonding to nitrogen in the air'. This is not actually what happens. Ammonia (NH3) will form in fresh manure and in many other materials - green grass clippings for example, if left to themselves, can start giving off a lot of ammonia gas. Ammonia can also dissolve in the water (moisture) that is present in the pile and form ammonium ions (NH4+). Is in constant equilibrium between gas and dissolved forms. Microbes will use it from the water, thus drawing more into the water from the gas phase and keeping it from wafting away. To accomplish this, you want plenty of 'browns' (leaves, straw, wood chips, cardboard, etc.) so the microbes will capture and use that ammonia while digesting the other stuff. It then becomes part of the compost (fixed nitrogen in the form of proteins, nitrate or nitrite salts). The nitrogen cycle is actually quite complex (we've hardly talked about nitrite/nitrate or fixation of nitrogen gas (N2) from the air!).
There is a lot going on in there. Fortunately we don't have to know ALL of it to make compost! But it helps to know some.