Slower, but not super slow. Latency is significantly higher, if you're used to ~10ms ping from your home to your data center.

Grabbing a page from my website over tor and over normal network:

    curl http://mywebsite
    curl https://mywebsite
    curl --proxy socks://127.0.0.1:9050 http://mywebsite
    curl --proxy socks://127.0.0.1:9050 https://mywebsite

Results in these times (tor times depend on selected circuit):

    0.028s / http
    0.063s / https
    0.394s / tor http
    1.079s / tor https

If I killall -HUP tor (force changes circuit):

    0.302s / tor http
    0.598s / tor https