I'm in the process of evaluating Eraser myself. So far, it seems very good at what it does. The one drawback seems to be the fact that it can't eliminate all traces of directory entries, and I'm not sure anything can under NTFS (except for a full disk wipe an reformat)--rather, it overwrites them with random data. But I'm not positive about this yet, either.
As for using eraser with no trace that it was there: Eraser does seem to require a system install (the help file lists all installed components). But if you want to run Eraser on a system with no risk of installation traces, I'd think the way to go would be to use eraser from a PE disk (e.g. a CD made using BartPE or similar program, which includes Eraser).
