I've ended up loving the show, and I decided to just continue on from where I started at season 3. Assuming my interest keeps up, I'll revisit the first two seasons after I'm all caught up with the present season, which I'm currently loving. As far as favorites for season 3, I'd say "Blink" and the "Human Nature/Family of Blood" episodes. Season four was just a slight bit less strong, partly due to the new woman companion Donna, who was fairly annoying at times, but it was still very strong. For a favorite from 4 I'd probably go with "Silence in the Library/Forest of the Dead". Excellent episode.
So I've gotten a fair bit into the fifth, and, while the new guy isn't quite up to par with the doctor from the last two seasons, who was absolutely brilliant, he does quite a nice job, and besides that I think the show has actually made considerable improvement, not only in the obviously stronger production and visual value (there was some iffy costume work/special effects in some of the previous episodes) but in the writing and consistency as well. So, even with the slight setback of lacking the previous doctor, I think it's actually possibly better than ever now. The new companion is certainly easier on the eyes and ears than previous redheads who have traveled with him, as well.
So, long story short, I'm totally captivated by the show. At this rate, I'll have finished it within a week or two. Maybe I should slow it down just a bit, make it last.