If your engine is running correctly, you will not get pre-detonation.

The reason the fuel is released before the spark is so that the cylinder stroke can compress the fuel, resulting in a more complete burn once the spark plug sparks. Diesels do this too, but their compression is so high it is the compression that causes the boom. While gasoline motors die and get blown apart by detonation, that is how a diesel works. If you were to spray fuel at the same time as the spark at/near TDC, you would have no power as the fuel charge would not be compressed. You have to remember, this all happens so fast, the naked human eye can't see it.

 

Good morning:
With direct injection you can run higher compression ratios ir higher boost pressure.
Fule economy is also better.
With Di the fuel is atomized & vaporized much better then when it is injected in the intake manifold.
Everything else being equal a DI engine will usually see a 10-15% reduction in fuel comsumption while producing more power
Here is good link that explains DI well.
Gasoline direct injection - Wikipedia, the free encyclopedia
Note the twin fuel engine FORD has using Ethanol DI with gasoline port injection

 

Forgot to add that most vehicles with DI use a Wide Range Oxygen sensors like the Bosch LSU 4.3 & LSU 4.9 sensors (NTK & Denso make a wide range sensor). These sensors will measure Air/Fuel ratios between 8-1 & 28-1 (28-1 is basically free air) whereas regular siwtching O2 sensors can only measure at Stoichiometry. When using these sensors they can run the engines very lean with DI for improved fuel economy whereas the engine would misfire with port injection.

 

Another bit of useful information here regarding the FORD ECO Boost engine series
Ford EcoBoost engine - Wikipedia, the free encyclopedia