I love actually building models, but hate removing mouldlines, especially when I know so many people who just don't bother.
I dislike priming, but it's got to be done and it doesn't require massive amounts of finesse, so I can do it last thing at night and paint in the morning, which is fun.
I love painting, but I hate batch-painting more than about half a dozen models at once. This is the reason I will not be revising my Vampire army and switching to the new models (that and I can't afford to).
I don't mind basing in and of itself, but it's often wasteful of materials unless I do a big batch (my basing matter comes in squeezy tubes... cursed, inefficient, inaccurate squeezy tubes), so I end up batch-basing... and I hate batch-anything, so I don't like basing. It also takes too long for PVA glue to dry, dammit.
It's a mixed bag, but I think basing is the part that bothers me the most. I'd happily buy pre-detailed bases and paint them if I didn't already have two large armies based in one style.