Hi,
I use Ilfotec HC or D-19 with Delta 3200. I use D-19 when I have to underexpose like crazy and/or want lots of grain or contrast (or both), and I use the HC in all other cases. I have tried various other developers, and could see how they might be superior for pushing (X-Tol especially), but not enough so to make my lazy ass want to keep them around when HC does the job just fine. HC is pretty much infinitely versatile, never goes bad, and is as convenient as it could get, short of being able to buy single-shot working solutions off the shelf. Its weakest point compared to other developers is its sharpness, and even then it is not "bad", and is not even noticeable once you go to 6x4.5 or larger. If I want real crazy tack sharpness, I simply do not use 35mm (and certainly do not use a super-fast film), with any film or developer, so I am not bothered by this.
There are some things to understand about Delta 3200 before taking off and running with it.
There is no box *speed* for Ilford Delta 3200. Nowhere on the box does it state *ISO* 3200. 3200 is simply part of the product name. The ISO is stated in the data sheet as 1000. This means that the film is an ISO 1000 film, period. Nothing ever changes that. Exposure and development can change the contrast and other characteristics, but it will always be an ISO 1000 film. You have to realize that limitation and know how to meter for it so you know what to expect from it and what not to expect.
Using an EI ("rating" the film) anything higher than its ISO of 1000 causes an underexposure. 3200 is on the box because it sounds good, and it is a usable EI when metering for the film (unless the lighting is just tremendously flat). What you are doing when you do this is simply underexposing your film by almost two stops. In other words, you cut out almost 3/4 of the light you want for a "proper" exposure. This means that if you develop normally, everything that would have been a shadow tone will end up pitch black. Your midtones will become dark greys, and your highlights will become midtones and light greys.
You cannot change the speed of the film except for very slightly. (This is the biggest misunderstanding about overdeveloping.) By overdeveloping, you can increase contrast, and thus make the film easier to print. However, when you overdevelop to increase the contrast, you make the compromises (of course) that you always make with underexposure and overdevelopment: reduced shadow detail, increased grain, and usually decreased sharpness.
The key to understanding why you overdevelop is this: Overdeveloping does not simply linearly increase the density of your emulsion. It increases density proportional to the amount of exposure received. Therefore, the less exposure a certain piece of silver gets, the less it will increase in density upon overdevelopment. What this means, simply, is that your shadows cannot be pushed, but your midtones and highlights can be. So, you are not increasing the speed of the film. You are simply adding contrast before the printing stage, because you know it will be underexposed, flat, and hard to print. The above mentioned side effects are what you have to sacrifice to get this.
For low-light shooting, the best (and only) way to minimize the grain and loss of sharpness drawbacks of the necessary overdevelopment is to use a larger format. (There's nothing to do about the shadow tones, as that is independent of format.) Then, of course, you become limited by aggravating f/2.8 max. lenses. There is the Mamiya f/1.9 medium format lens, but still, you see the aggravation of having to compromise something at every turn....since with an 80mm lens and a big-ol' mirror slapping about, you are having to use faster shutter speeds to shoot hand held. In the end, you realize that nothing beats 35mm for low-light hand held work, and just deal with the drawbacks.