I must admit that there were times and episodes when I wondered if Garak were going to end up on the Cardassian side in the long run, as in "Profit And Loss", "Second Skin", and "The Die Is The Cast".
Fortunately he didn't do that. Instead he became a valuable help to Sisko and his crew during the Dominion war.
The only time I found him downright disgusting was when he tortured Odo in "The Die Is The Cast". He was also very rude to Ezri in "Afterimage". Otherwise I found him to be a charming, cunning, mysterious and interesting character which have made him one of my favorite Star Trek characters. I have actually toyed with the idea of creating a Garak website.
By some strange coincident, I'm just re-reading the book "A Stitch In Time", a very interesting biography about Garak written by Andrew J. Robinson, the actor who successfully portrayed garak in the series.
As for his return to Cardassia in order to build up a better Cardassian society, I would like to see him return to Deep Space Nine as Ambasador to Bajor and Deep Space Nine. Then we would have him back in future books while he still could contribute and help the new Cardassia.