The writing, and the books themselves, do get better. I've heard people say the series really 'starts' (as in, gets that Dresden feeling, really gets going), in Summer Knight (#4), though some argue it really finds its footing in Death Masks (#5).

That being said, yes, there are often little inconsistencies. Especially with things like weapons, and the heights of characters. And Harry doesn't ever really grow out of that 'being Harry' quality he's got, that leads to some questionable decisions. This of course is a main component of what makes Harry Harry, so it works, but...

All of this to say, fantastic series, don't give up on it because of the earliest books.