I haven't used OmniPage but it's gotten good reviews i think.
I am, however, a big fan of PaperPort. Now i have to warn you i haven't really compared it against other programs, so take this with a grain of salt, but it's one of those programs that just feels right to me. I don't do too much scanning but everything seems intuitive to me, and i've been very happy with it. Nice basic tools for straightening scans, organize scans, etc.
Recently i found an abandoned scanner with an ADF (automatic document feeder), and ScanSoft handles it so wonderfully that i wanted to hug the program. Scans in some sheets, lets you then reverse the stack and scans in the other side while properly collating it, etc. very nice.
Here's an image of the multiple (ADF) interface:

Last caveat: I do *not* do heavy duty and frequent scanning.. there are a ton of features in PaperPort i never use. I imagine that if you do a ton of scanning then you'd really want to test other programs and find the one with the most efficient workflow for you.