Too long is horrible, short with no white is acceptable. A little length without being extreme is probably best, imo. I like the shape being a natural curve like the fingertip, pointy is scary, square is some kind of style that just isn't my preference. I don't think it matters much at all though, as long as they aren't exaggeratedly long.
What kind of condition they're in is something I'd pay more attention to. As long as there isn't something wrong with them, they are nothing to concern yourself with, imo. I don't know about other guys, but I probably wouldn't really notice if you had a great manicure.
Squoval. That is a word used to describe a nail length that is about 1/8" past the fingertip and has a squared-off shape but with the corners slightly rounded so they are not sharp. This shape will make just about any color look great on your nails, including french.
Ideally, your nail end shape should mimic the shape of your cuticle so the nail looks somewhat balanced. Length has something to do with this though, since you could get by with squared off tips if your nails are longer.
A real turn-off is the shape f the 50s, a sort-of pointy-round shape that make your nails look like claws. It looks dated and tacky, like someone glued cheap fake nails on.
And forget short stubbly nails. Leave that for the guys. When I see women with really shrot nails wearing nail polish, I can;t help to think that they look like guy-nails with paint. Women's hands look best when their fingers look long and dramatic (feminie).
For toenails, keep them just shy from the end of your toes and mostly squared off. Pointy toenails make you look like a hobbit.