I use a plextor 24/10/40U and have had no problems. No coasters, no headaches. However, it is not functioning with the CDA 5 beta. CDA does not even recognize that it is on the system. The CDA beta support team has been very responsive, but not yet successful. The plextor has worked fine with all other burn software I've used. (Including various packages on a mac)
Updated information. The problem appears not to be with the plextor, but perhaps the Adaptec USB2/PCI expansion card or its drivers. The plextor works fine (although only at 5x) when plugged into the onboard USB 1.1 ports that are part of the Compaq mother board. CDA support and I are looking into updated drivers for the adaptec. This is all very confusing as nothing else is having problems with the adaptec USB ports.