As someone who watched the entire series on live television, I can share with you some of my insights.
SPOILERS....... (for those who have not seen the series)
Season 1 had, what I consider to be the best ensemble, casting, and writing of the entire the series (although the writing after Sandoval's Run (a huge high point of season 1) would begin to give us a glimpse of what was to come). THe chemistry on screen with all of the characters (Boone AND DA'AN together specifically) was a high point. Lilli, Augur, Doors, and especially Sandoval where are pivotal parts of the series that exemplified the potential of greatness that many (myself included) expected for this series.
Again, this is not to say that there were no clunker episodes that I wish could have been jettisoned, but for a first season, it showed much promise. I remember people complaining that it was too cerebral or not enough "action." I also remember that people complained about some of hte special effects (which were are there early stages of development for television). Despite some of these complaints from my friends, I thought that there were some great episodes that made you question the moral ambiguity of the characters and their motivations. Boone was truly caught in the middle of a world where the Tealon's and the Liberation were truly ambiguous. The slow reveal of who and what the Tealons were about were great high points for series 1.
The ending of season 1 left me completely shocked since I was not aware of what was to come. It definitely picked my interest to come back and see the further adventures of EFC.
What came after season 1, was for me, a disappointment
Boone was "killed off at the season 1 and his death was "confirmed" in the beginning of season 2 when they brought in the character of Liam Kincaid. You also had major upheaval since most of the writers and producers left the series (such as Richard Okie). The series was never the same and Tribunes meddling (liek what they did to Anromeda) was to make it more "action packed" while dumbing down the series.
Unfortuneately, most of the cast left throughout the series. Lilli went on maternity leave and was written out of the show at the begining of season 3. Augur left at the beginnig of season 4, Doors was killed midway in season 3, and the total blow to the serieswas at the end of season four when they got rid off Da'An and Zo'or (and yes even Liam).
Season five, IMHO, was an abomination of the series. All of your interesting characters (except for Sandoval) were gone. Renee Palmer, Lilli's replacement and series 5 lead) became an "ubber-buffy the vampire-esque" character that was unrecognizable (besides I was not a fan of her acting). The Tealons were gone and replaced with the Atavus, vampire wanna-be aliens that were suppose to be the progenitors of the Tealons and Jaridians. Although the tried to tie back much of hte shows mythology to this new season, it really was another show and should have been so. Although certain characters (Boone and Zo'or) returned briefly, they were unceremoniously gotten rid of (Zoor, as an Atavus was killed in a shuttle fight with Renee and Boone was "killed off-screen"). Liam at least did return for the final episode. BUt by this point it was just plain awful.
Postings on this board and others suggested that most of these changes through out the series run ere due to financial considerations. Although I understand the importance of staying in budget, I wish the writers would have found ways to improve the writing/stories so that they could stay within budget and keep the original cast (and the season 2 additions) and toss out the expensive CGI. But the writing, especially in the later seasons (season 5) really declined and did not help the series in any way.