Well read/write speed really isn't important for drives that operate as the main OS/boot devices. However an average drive today...between 500GB-1TB will have reads of around 100mbps. Older drives go even lower.
A good MLC SSD like an Intel X25-M has reads of over 250mbps...mine has went up to 276mbps on some tests but mostly stays in the 268mbps range. Higher end and faster drives can get rates of faster, the Micron C300 series can get 300mbps+ and PCI-Slot OCZ 1TB 500GB+ SSDs can get to 800mbps reads and 600mbps+ writes. Usually hundreds of percent faster then HDD's.