I've never heard of square needles. Can you at least provide a brand name, or a link to a photo or a web site where we could see them?

http://www.sweitzerscountryside.com/newproducts.html
They are made by Kollage. Above is a link to check.

The circular cables from KnitPicks don't have memory, so you can knit with them immediately, just as those K-Kables are advertised to do.

As for the square needles -- I would think they'd be uncomfortable to hold when knitting for long periods at a time.