Martha was my least favorite, but part of that is just with her being after Rose. She has a lot going for her, but I felt like they focused too much on her being in love with The Doctor and pining after him. That was the most annoying thing about Tennet's run to me: everyone just seemed to fall in love with him. Martha is in general a good, strong character though.

It's been a while since I've watched the episodes with her in it too, so I could be remembering things wrong as well.