I have a Mavic Open Pro 32 spoke wheel that I used for commuting and cyclocross this fall into the shop the other day, and when they called to tell me it was ready, they said something to the effect of "well, we got it as true as we could. You know it was in pretty bad shape. Also, your brake surface is pretty worn, you should ask us about what rims we have in stock!"
Although it isn't prefectly true, after they worked on it it is in great shape. You can definitely feel that there is a groove worn into the brake surface, however. Should I seriously be considering another rim at this point? I would just as soon ride this rim until the braking surface is worn paper thin