We are in the same situation. We have 4 bonded T1s for 6mbps looking to upgrade to 10mbps Ethernet over Copper. Ethernet over Copper(EoC) usually means that the ISP is delivering an Ethernet connection over standard Copper wires. The twisted pairs that your DS1 lines use now are Copper wires.
This article claims that EoC ranges from 1 to 45 mbps, varying based on Distance. 10mbps is the most common speed that I have seen offered from XO, Verizon, and Broadview.
I would expect(not based on facts, just assumption) the SLA, uptime, reliability to be very similar to what you have now. This is just a different protocol operating over the same physical medium. SLAs and Time-To-Repair will vary based on your contract, but I would expect these to remain the same/similar especially if you are staying within XO.