I like interchangeable needles and think I've finally decided on the wood tips, I'll get them from KnitPicks or WEBS, the cables and tips of both brands work together, I have the try it set from each. One thing I like about them is that when I'm ready to switch to a smaller needle for ribbing, it's really easy to just change the tips out. I've come to think of them as needles on a leash...as long as I have one of them the other is still attached and hasn't been eaten by the chair cushion, slid off to the floor, or fallen out of my knitting bag and gone who knows where. Not losing one needle probably saves me a lot of money.
I should never overestimate my basic arithmetic skills.