I really like aluminum needles (I've never used any other material, though).
For knitting in the round, I use DPNs. I don't like circular needles. I once said I'd give circular needles a try, but I took it back: I simply don't like circular needles.
Well, I guess I'm in the minority, but all I have are Boye needles and I like them just fine.
I have a Boye 4 DPN set (3 1/8 mm), and I really like it!
I've been looking for more Boye needles, but, I just can't find them. Knitting is not a well known art here in Colombia (at least not that I know of).