Texeira is a short right-hander that doesn't light up the radar gun, so exactly the kind of pitcher overlooked all the time. His production is unquestioned though. Kanekoa's career ERA is under 3.00 in the minors. Granted, he is yet to play above AA, but that's still quality production.
Texeira relies mostly on ground balls to be productive. He projects to be fairly hittable in the majors, but ground balls for the most part are harmless (especially with a guy like Jack Wilson at shortstop). Looking at his numbers, for some reason he generated way more ground balls facing left-handed hitters last year. I don't know if that's a trend with Texeira or not, but that may make him an option to use as a quasi-specialty lefty, even though he is right-handed. Realistically though, he will probably either be a middle reliever, or returned to the Yankees.
If you are interested, you can find all the Rule 5 draft results here. The Mariners lost only one player, 1B Marshall Hubbard, in the AAA phase.
Of players picked in the MLB phase, here are the ones that I think have a chance to stick: LHP Ben Snyder (TEX), LHP Edgar Osuna (KC), LHP Zach Kroenke (ARI), RHP Bobby Cassevah (OAK), LHP Chuck Lofgren (MIL), LHP Armando Zerpa (TB), and RHP Kanekoa Texeira (SEA). The most intriguing of the bunch to me are Snyder and Cassevah (looking at Cassevah's numbers, I'm pretty sure he's a submariner). Texeira seems to be the safest bet of the bunch, though I wonder if he is a year away from being truly ready.
The Mariners also picked someone in the AAA phase, RHP Terrence Engles. He was quite good last year, but awful the year before. Did he find something in 2009? The numbers are so drastically better across the board you would have to think so.
And there you have it, the Rule 5 Draft. Teams loaded up on arms, which is the smart thing to do. No reason to spend money on middle relievers when several can be found for cheap.