They're excellent (all three trilogies), and on a par with "The Shadow Within" and "To Dream in the City of Sorrows." Some people like some of the trilogies more than others. Personally, I like the Centauri and Technomage trilogies more than the Psi Corps trilogy.
The Centauri trilogy has a couple minor mistakes dealing with the year part of some dates (e.g. 2266 being in the books when it should have been 2267).
The Technomage trilogy (Book 2, pages 317-321) has an error where it intersects "The Geometry of Shadows" (specifically the end of the episode, when the Technomages leave). It's an issue of timing, and where a certain ship explodes. The book needs to be fixed here, because the episode is "canon." I've had email correspondence with the author about it, and she (somewhat reluctantly) agrees, though exactly how to fix it remains up in the air (and I suspect will never be done). But, she knows about the problem. Other than that one real problem, I think the Technomage trilogy is great.
Have you watched Crusade? Remember the Technomage trilogy takes place from 11/2258 to 1/2261, "A Call to Arms" took place 12/2266 to 1/2267, and Crusade from 1/2267 to ?/???? (We only saw thru ~9/2267. The unpublished script "End of the Line" would have been in 12/2267.) As a result of this, you might not think that the Galen of the trilogy matches up with (or makes a linear progression to) the Galen of Crusade. In some instances, the Galen of Crusade seems more tentative than the Galen of the trilogy (e.g. at the end of the trilogy). I don't have a problem with this because I can see in-the-story reasons for the differences. /forums/images/graemlins/smile.gif
FYI:
Dark Genesis - The Birth of the Psi Corps (2115-2189)
Deadly Relations - Bester Ascendant (2189-2258)
Final Reckoning - The Fate of Bester (2271-2281)
Legions of Fire - Book I - The Long Night of Centauri Prime (2262-2267)
Legions of Fire - Book II - Armies of Light and Dark (2267-2273)
Legions of Fire - Book III - Out of the Darkness (2274-2278)
The Passing of the Techno-Mages - Book I - Casting Shadows (11/2258-12/31/2258)
The Passing of the Techno-Mages - Book II - Summoning Light (1/2259-2/2259)
The Passing of the Techno-Mages - Book III - Invoking Darkness (8/2260-1/2261)