I'm quite enjoying all the new series.
Eccleston was OK, but compared to Tennant/Smith seems a little sub-par, perhaps because he did not stick with the series long enough.
Rose...she annoyed me, as did Mickey. The love-triangle thing that developed dragged on and on and, IMO, detracted from the series overall. Mickey was just generally useless.
Tennant was a pretty amazing Doctor, and a fantastic actor - however he, as it seemed to me, was too weepy most of the time. Having Catherine Tate as the companion worked really well, she off-set the Doctor nicely as well as providing a contrast to the general darker tone that the episodes were taking. Martha is probably my least-favourite companion ever (including the retro episodes).
Smith has a hard time, having to follow Tennant. However, I think he makes an amazing Doctor, and is probably my most favourite yet. Why? He may not be on an acting-par with Tennant, but his oddities and quirks, as well as general appearance, making him seem more alien that the Doctors have been previously; and his character in general lends itself well to a space-and-time-travelling super-intelligent, but ultimately lonely, character.
Amy swings between annoying and all right - she has her strong episodes and weak episodes. It is getting annoying that Rory seems to "die" all the frigging time, but he does have an awesome backstory and several moments of badassness that make him a somewhat lovable character.
Episode-wise, I think the last two series have been a mixed bag. Some have been absolutely amazing, some have been hysterical ("The Doctor's Wife"), and some have been dire (this most recent first-half of "Living Flesh - where nothing seemed to have actually happened and is just extended filler for the next episode). The foreshadowing is horrifically obvious compared to what has gone before, but I am hoping that is something that will be improved - but you can live with it when you remember that this is a series for absolutely everyone, from children to those who watched the originals with their own children.
So yeah, I'm liking the new Dr Who as a whole, and Smith's Doctor seems to be going quite well.