As long as it's not flaking off I would think so as -- however, I wouldn't recommend using it in the oven with high moisture foods, or being used for cooking high acid foods as both those things could start undoing the work you've done so far. So it's probably best to wait on those uses until you've used it enough to build a a nice layer of seasoning.
I also suspect that continued use and cleaning the pan (and oiling it) after every use will eventually take care of the remaining rust. One thing I've learned is that cast iron responds well to being used frequently, and cared for in an appropriate manner. If that's done, then I'd say cast iron can actually become easier to clean & care for than most other types of cookware.
For example the griddle I use at least once (if not 2-3 times) a day has such a nice non-stick surface on it that I rarely have to clean it after cooking. Just take all the food off, turn off the heat, spray a bit more cooking oil on the hot pan and then go enjoy my meal. About the only time I need to do more is if I've been cooking bacon and need to let the grease cool so I can scrape it off without burning myself. If on some rare occasion I need to wash it, then a simple brush with hot water (no soap) will get everything off. Of course after washing and drying it, it gets a layer of cooking oil wiped on everywhere it got wet (doesn't need to be anything more than just a thin sheen).
Cast iron pans/skillets can also be used to good effect for baking/cooking in the oven (if rust free at least). I use one of mine for cooking leg of lamb which with the fat that melts off also seems to help season the cast iron while the whole thing cooks. So I get a tasty meal and improved cast iron. Shepard's pies can also be cooked with cast iron in an oven.
General rule that I've observed from my own usage is that cooking/baking with fats/oils on the cooking surface helps build the seasoning/non-stick surface, and watery or high acid foods (e.g. tomato sauces) can/will strip the seasoning off (much like soaps will as well). That being the case once a solid seasoning is built on the cast iron, it's just a matter of balancing the cooking done in it (which is one of the few reasons I still have some cookware that isn't cast iron).
