Lae'zel? Really?
She's one of the better Gith characters.
Of course, initially, she's got a lot of the traits of Githyanki, due to the way their society works and Vlaakith's influence.
But she's softer than most Gith and occasionally shows a much softer side to her character. She's not inherently heartless, she was raised that way (It's the crux of Lady Esther's project to raise a Gith without imprinting on a violence based culture)
The fact that she's open minded to things that shatter her entire way of life, shows she has much more depth of character than most Gith who'd simply cut down anyone who didn't acquiesce to their every ideology.
As far as appearance goes... For the most part Gith look less appealing because of nature to be in a near permenant scowl. I know that there's a dialogue when approaching the Trielta Crags waypoint where Lae'zel isn't scowling and she looks really cute.