I know with mine (4490) I have to use the unsharp mask feature. ICE is just for dust and scratch removal and doesn't work well with standard silver based B&W film (the silver in the emulsion can be mistaken for dust since it blocks infrared radiation). But for scanning color work, it does miracles.
The problem with flatbeds is that they scan through the glass. Thus you can get a bit of diffusion of the image. I always scan in 16 bit mode to get the maximum amount of color information. That way, when I adjust the histogram in Photoshop, I don't loose much.
I also like to adjust the scan exposure first. But make sure your screen is well calibrated
Exposure shouldn't affect resolution. I don't tell the scanner what size image I plan on getting. To get my DPI setting right, I use
ScanCalc. It's free software and works wonders.
If you get blocky images, look more on the resolution side.
Now, if you want the ultimate in sharpness, you can always get a dedicated film scanner. These have an autofocus mechanism that ensures the highest quality. While going through an old magazine where they tested a 520GBP (2005 price) Minolta DiMAGE Scan Elite 5400 (35mm scanner) they got on eBay and compared it to a Nikon D50. They say the scanner will do a 41 megapixel equivalent from film. Looks like a very nice piece of kit.
But if you're on the cheap side (like me), and you want those photoshop images to be tack sharp without the usual artifacts that come with the different sharpen tools (like halos around hard edges), you might want to try out LAB sharpening:
-Take the image and switch it from RGB to LAB color.
-Open the Channels palette (windows-channels)
-Select the Lightness channel
-Apply an unsharp mask using a value of between 100-150%, a pixel radius of image resolution/200 and a threshold of zero
-Return the image to RGB mode.
I do this after all work on the image is complete. I save in either PSD or TIFF when the image is getting worked on. Saving the file over and over in JPEG mode degrades it quite a bit. If the image came from a JPEG, I save it as TIFF so as not to damage the image anymore.
Hope this was of some help...