The cuttings boulders are quite short meaning many lots of sit starts, and the boulders are quite spread out and difficult to walk between however there is the occasional fun problem that is worth the scramble / search.
There are a few other isolated spots included in the CC Portland guidebook including a spot above Blacknor that I have tried.
Generally speaking people go to Portland for the sport climbing and it is far from being a bouldering mecca. That said if you can't get hold of a belay partner or are looking train a bit of extra power there is plenty of fun to be had.
In reply to hudman: Portland bouldering is good, but not the best. The main down side is the lack of height and poor landings. The Cuttings is the best area. You can download a guide from the link below. There's a good range of problems but not much above Font 7C. If you live down south then it's worth a trip. If you live up north then there are better options. From Reading it's borderline. Do both. http://www.rockfax.com/climbing-guides/all/portland-bouldering-cuttings-boulderfield/