The horizonatl line, as noted in the 101 paper, is the ideal. Not all apps will reach that ideal, or to reach it they might require prohibitively large amounts of heap space. I think that what you have here looks really good, you should get major collections only occasionally, which is the goal.

You could increase the heap size (if you have free RAM) and the new size accordingly, that might make a better graph.

Finally, the 101 and 201 papers are fairly old (I think JDK 1.5 was not even out yet for the 101 paper). My recent experiments showed that JDK 6 will automatically adjust the new size to about 1/3 the heap size after a dozen or so collections, so setting new size in JDK 6 is not as important as it once was, so I am no longer recommending setting new size for JDK 6 or later. (My Java performance seminar at this year's CMG Conference has a slide showing how each JVM from 1.3 to 1.6 adjusts, or fails to adjust, the new size over the course of time.)