Australia's ABC2 channel has been playing catchup the past few months. Tonights episode is The End of Time Pt 2, being Tennant's sendoff.
I have to say, the first time watching this series since it was originally aired really has changed my impressions of the various partners.
I do find, with hindsight, that Donna is the best of the modern companions. I'm not well versed in the old school Dr Who people, but Donna is a far more interesting character with a better chemistry with the Doctor than any of Rose/Martha and even Amy. Amy is a close second though.
Also, whilst this is pure wishful thinking, after the wonderful Eleventh Doctor finishes his run, I really really really hope we get to see Benedict Cumberbatch as the Twelfth. Either him or Martin Freeman. Failing that, Andrew Scott (Moriarty).
John Simm, who played The Master, would have also been an excellent Doctor, given how well he played Sam Tyler in Life on Mars.