kacheng, your DNS problem is not related to this bug - you should file another one. As for the slowness compared to the official version, that is most likely due to Pango.
For Rotund, it is possible that Xgl makes a difference here. If I recall correctly, Xgl accelerates cairo - this might make pango faster. However, this does not fix the problem, as Xgl is far too unstable to be standard in Dapper, and I don't think it will be standard in Dapper+1 either.
For mannheim, please read the comments about Pango. That is most likely your problem.
kacheng, your DNS problem is not related to this bug - you should file another one. As for the slowness compared to the official version, that is most likely due to Pango.
For Rotund, it is possible that Xgl makes a difference here. If I recall correctly, Xgl accelerates cairo - this might make pango faster. However, this does not fix the problem, as Xgl is far too unstable to be standard in Dapper, and I don't think it will be standard in Dapper+1 either.
For mannheim, please read the comments about Pango. That is most likely your problem.