Awesome. The Eisenhorn omnibus is the only Dan Abnett book I've read, how do the others compare?
Eisenhorn is probably the single greatest thing Abnett has ever done. Everything worked perfectly with the sole exception of maybe the last fifty pages of the last book (just felt REALLY rushed).
I enjoy his Gaunt's Ghosts series, but I am one of the first to admit that Gaunt suffers from Mary-Sue syndrome. Although, the recent arcs have showed Gaunt's weaknesses and failings (and also promoted him to a near messianic figure).
But the best thing to come out of the Gaunt books: Double Eagle. It is basically to Aeronautica Imperialis what pretty much every other 40k book is to Warhammer 40k. A very good read, and very fun characters.
Note: If you do decide to try the Gaunt books, I suggest reading Book 2 before Book 1. All you will have "spoiled" is that some bad **** happened at Menazoid Epsilon, Rawne wants to kill Gaunt, and that Varl and Domor were both injured. Abnett's main weakness is that he can't write introductions. As a result, the first book is really random and chaotic the first time through, whereas book 2 (which is really just a collection of the short stories that spawned the Tanith First and Only) is essentially a very long intro.