They've been very reliable for us. Network is spiky (12-20MB/s at times), but otherwise, compared to roughly equivalent VMs (lscpu, /proc/cpuinfo, etc.) they are hands-down faster than AWS. In the limited testing we've done on AWS SSD AMIs (optimized for cluster compute), AWS wins on network and CPU, but at literally 10X the cost.

Also, see: http://serverbear.com/9806/digitalocean for interesting benchmarks over time (with all the standard caveats, yada yada).