Having now re-established that I know the relationship between needle sizes and gauge, I've finished swatching.
First off, let me say that achieving gauge with yarn that is toying with you is in excellent way to interview needles. Thanks to the Divine Though Blogless Elizabeth's unflagging generosity, I've got the opportunity to play with a whole set of the Darn Pretty Interchangeable Needles. Because I had that brain glitch, I wound up knitting with several needle sizes of them. This is more important than one might think, since a knitting needle's joy lies in a delicate combination of material, finish, tip, size, warmth, flexibility, and (in the case of circulars, the all important join). That combination is subtly different as you go from one size to the other. Thus, when considering a set, it's REALLY worth it to try multiple sizes before committing!
I started my interview with the recommended (by the pattern) size 5's. Right off, I loved the join and the finish, and the warm subtle flexibility of the wood. The tip was pretty nice (not stellar, as I personally prefer sharp tips, but quite nice). I was even fonder of the 4's (I found this tip sharper, which is a clue that I missed about the tip/needle size behavior), but I was less enamored of the 6's, because the tip gets blunter and blunter as the needles get larger. (This is pretty standard - one doesn't really need a super sharp tip to pick up thicker yarns, but the 7's blunt tip would make me nuts if I were trying to knit cables or lace). For straight up knitting, I found them fine. More than fine.
The join is marvelous! Not only did I never once struggle with the join between the tip and the end of the cable, the join between the cable and the needle itself is bloody brilliant. THAT join spins ... which means that the inevitable twisting and winding that one does while knitting does not translate to the tip/needle join, and thus the tip never tries to come undone!
For me, the tips for this set may be a deal breaker (but they do come with lace tips). I like cables ... especially on worsted weight yarns, for which I'd be needing the 8's or so. I also like playing with the airier fabrics you get by knitting fine gauge yarn (like, oh, Koigu) with a larger needle (like, oh, the 6's I'll be using for this project). And I like lace knitting -- another place one uses needles that are larger than one might use for a "regular" fabric.