Ok, admittedly Photoshop is homebase for me. However, I have been using Illustrator lately and am having trouble with something that seems quite simple.
When trying to move objects around with the arrow keys (pixel-by-pixel nudges in PS) they seem to move by much more than one "pixel" at a time. For example: If I have two diamond shaped objects, there are many times that it is IMPOSSIBLE to get a corner of one diamond and a corner of the other diamond to touch exactly at their tips. They always are misaligned and have an apparent gap.
Specifically, I have an illustration of a leaf, with another illustration of the center vein of the leaf, but I cannot for the life of me figure out why I can't get the tip of the vein to match up exactly with the tip of the leaf (there is always a small gap between the two).
I thought Illustrator was supposed to be more accurate and practical for this kind of work, but I have none of these problems in Photoshop.
View>Smart Guides are your friends; if you drag one by the Anchor Point, they will say anchor point when you are there, on top of the other.
It may also have something to do with Align to Pixel Grid, if you have it turned on; you can see that in the Transform panel.
Apart from that, you should have a look at Edit>Preferences>General>Keyboard Increment, which determines the nudging steps.
Unfortunately the problem persists. If I zoom in, I can move objects around in very small steps with the cursor. However, the cursor is not very sensitive and it can become mind-numbingly difficult to get something EXACTLY where you want it with the cursor, thus the use of nudging. Nudging at this level, even with the increment set to the smallest measurement possible, still sends objects much further in any particular direction (like, 5 - 10 pixels-worth) than does the cursor, basically defeating the purpose.
VERY frustrating. I have one program that has pixel-perfect accuracy but only creates rasters, and another that will create vectors but has the accuracy of a drunk Boieng 747.
What happens if you use Smart Guides? Does it work or jump away?
I am afraid there is a host of snapping options.
You may try to look into the Helpfile and search for Snap.
Maybe someone with a newer version will give some suggestions.
Can't really help, but I'm having this exact problem. I'm using CS 6, and I can't seem to find the "Align to Pixel Grid" option. Adjusting the nudge distance in preferences doesn't help either (I have it set to 0.0002, and its moving 1/16" when I nudge).
Try the Transform panel. It's only on by default if you use one of the Web presets for your document setup but it can be on for individual objects even if you copy them to a new, clean document.