I bought an Oliso when they first came out and though it was pretty expensive at about $100, the feature I loved was that you don't have to bend your wrist backwards to set your iron upright every time you take your iron off your project--you just push it aside and little feet come out of the bottom to hold it safely up off the ironing board. I haven't felt that it gets hot enough, however. Maybe that's just mine.
In general I'd just buy a cheap one with lots of holes--and use it till it conks out and then toss it and buy another.
As a side note, I've found that those Mr. Clean-type sponges that are white on one side and blue on the other do a great job of cleaning cooked-on starch, etc. off irons. Use the white side to scrub it off and the blue side to soak up whatever's left.
Dana