I love working with circular knitting needles. While I still use dpns sometimes, I more often opt to employ the Magic Loop method for small circular knitting. The Denise Interchangeables are a great set. They are plastic, the lengths of cord can be combined, are lightweight, have a nice case, have smooth joins, lock securely with a half-turn, and the tips are not too sharp. Knit Picks interchangeable needles are called Options, and go down to a US 4, and must be tightened with their little key to keep them securely joined to the cord. They come in metal or wood. I own their metal set and have some of their fixed circulars, too. I really like my Knit Picks needles. They are offered at a reasonable price. They have pointier tips, and the joins are great. I ordered one fixed circular of their wooden needles (Harmony). I like it pretty well. One day I might purchase the Harmony set of interchangeable needles from Knit Picks. I understand that after the first of the year, Mary (The Knitting Zone in Laceys Spring, AL) will have Hiya Hiya interchangeable needles. I do not have any Hiya Hiya needles, but people I know who own them really like them. I am not much of a fan of Boye interchangeable knitting needles. The cables are too stiff for my liking, and they also require the little key to tighten. I like my Denise set and my Knit Picks set. I find that different needles suit different knitting projects. Features of a given needle can be an asset on one project, and a liability on another. For example, my Knit Picks are great for lace or cabling without a cable needle with their nice, pointy tips. However if I had a splitty yarn, I might prefer my Denise needles. Also, the nickel Knit Picks needles are so slick that the yarn slides along nicely. Still, there are times when I need a little grab along my needle and prefer the plastic Denise set, or the wooden Harmony would be a better choice. Of course, personal preference is key, too. I was discussing the Knit Picks needles with one knitter, and she disliked the pointy tips and felt it to be a drawback, while I was singing the praises of the needles over this very feature.

my fav circulars used to be addis, followed by inox express. i haven't tried the knit picks set(have no need for one yet) but do enjoy their regular circulars. they knit smoothly at the tip and at the joint. that said, i had one odd one which was not quite smooth at the joint out of many others which were good. i like their price. my denise works great too but they dun have smaller needle sizes. good luck!

I've tried many kinds of circs made from lots of different materials. My two favorites so far are the addi lace needles (brass colored with pointy points that I love) and the knitpick options. Of the two, I prefer the Addis, they feel lighter to me, I love the color and the non-reflective surface, since I do a lot of knitting outside. I also like the bryspun circs. They're nice and light, not too slippery, but the cords on the ones that I have do tend to pull out after a while. I fixed it with a dot of glue and it seems to be holding but it is a consideration. Plus, sometimes they plastic is too grabby.

As for the point protectors for dpns, what I usually do is fold the project so that the needles line up and put one protector on all the needles. I've also used a pakage of mechanical pencil/pen erasers for individual needles, and they worked well, however, I had the ones that were intended to erase pen and I think that the grit in the eraser was hard on the tips of my needles, YMMV. Cork also works well, but can be unweildy for one needle unless it's cut down. I've been meaning to pick up an eraser stick, intended to refill one of those eraser pens, and cut my own point protectors out of it but haven't stirred my lazy self enough to do it. :)

Oh, one other tip I have heard but have not tried, to prevent the stitches from falling off you can wrap a rubber band around the opposite end of the needle. Something like one of the rubber ponytail holders (they sell them in tubs at wal-mart) that are smaller than the typical rubber band would work, I think. I've seen them marketed as ouchless because they don't have the drag/stick that regular rubber bands do, a plus when working with fiber. They make good stitch markers too.
If nothing else, I'd think a rubber band might be a reasonable replacement for the yarn ties in your current method.

Would a simple eraser stuck on the end of the needle help?

Instead of putting things on the ends of the dpns, get a piece of fabric and a rubber band. Scrunch up the knitting in the fabric and rubber band the fabric into a pouch/bag. The knitting can't spread out enough to fall off the needles. Elizabeth Zimmermann mentions doing something like this in one her books, and I think Galina ....? of the Orenburg shawl books, mention that shawls in progress are protected this way too.