There are at least two other choices. One involves some balls that slip onto dock lines, and allow the line to roll up and down a pile. I forget the name, Tide Minder, maybe something like that. Some dock neighbors use them, like them... but looks to me like the extra weight on the line would be making it a bit of a deal to keep it all from falling in the water. Also, the resulting line angle doesn't look as useful as with the Tide Slide; the weight of the multiple balls tends to make the line droop down the pile...
The other is a newer (to me) idea, a ring that slides over the pile and either floats or can be elevated on the pile. Google Pile Ring. I have a sample ring, and decided it didn't suit us too well. With the ring floating, the angle of line from ring to bow cleat (for example) wasn't useful, and then when we leave the slip all the weight of the line tends to want to drop that line down into the water. I also tried elevating the ring, about halfway up the pile, but it didn't seem all the elegant to me, and it also didn't really facilitate a tight tie-up all that well.
On paper, the Tide Slide looks about best. They're pretty proud $$$ of 'em.
-Chris