From the moment I first saw them in Episode I, I was not impressed by battle droids. They just...well, look goofy—like a skeleton with a banana for a head. Not exactly the most imposing things in the galaxy. Some backstories I've read for them say that they're supposed to look like skeletal insects, but I don't see it. When you throw in their annoying 'roger roger' voices, they lose even more respect. Subsequent movies and cartoon series do little to better this impression. In fact, the droids seem to be played for even more 'comic relief'—offering snarky comments that seem totally out of place.
The saying is that a person can be measured by their enemies. What does this say about the Jedi, then, when they're hacking down hordes of goofy banana-headed, cowardly and inept opponents. Kinda makes them look a bit silly, too. I just do not understand why the droids were designed like this, from a film-making perspective—unless they truly were just for comic relief. In that case I think they failed (except maybe for 6-7 year olds).
On the flip side of this were the Destroyer droids, and later the 'super' Battle Droids. Both of these designs seem suitably menacing enough. The first really does have an 'alien-bug' look to it—and they were shown to be feared and deadly. The latter cuts a menacing, hulking profile that I would more readily equate to combat 'hardware'. But sadly enough, when they fight alongside the banana-head droids, they seem to call even more attention to the silliness of that design.
If the film-makers had given the battle droids a more human-like 'skull' head, I think my perception of them would be quite a bit better. Likewise, if they focused more on the 'inhuman' precision of the things, rather than trying to give them 'wacky' personality, they might actually seem like a threat. Again, one of my biggest peeves with the prequels is their wordiness. Why did the droids have to talk at all? Couldn't they just communicate via radio with eachother? in binary? Anything other than that 'roger roger' crap.
In one of the forums I frequent, one of the posters commented how the personalities of battle droids might actually have an explanation. They're cheap—meaning their programming and 'personality-matrix' probably isn't the best. If they go for a few months without memory wipes, perhaps they just naturally develop snarky and self-interested attitudes—just like R2's supposedly get quirky and stubborn. Well, its an explanation at least.