My own recommendation is to not bother with a controller at all, and use your #1 eyeball instead. There's a handy window on these ovens.
I did build a controller myself some years ago, but I only use it to monitor the temperature, ot does no profiling itself.
Turn the oven on, wait for the solder to melt across your board, leave it on for a further fine or ten seconds, then off, and open the door to let it cool at a reasonable rate. Having an optional internal temperature readout is handy to confirm your eyes are not deceiving you. I also make sure the area's well lit with an illuminated magnifier helping particularly in the case of monitoring smaller parts.
Problem is you have no control of the temperature profile. The effects from an uncontroller temperature profile can be:
1. Insufficient soldering and dry joints
2. Mechanical stress build up on components from unequal temperatures resulting in early life failures
3. Voltage de-rating of some devices, like tantalum capacitors
4. Uneven temperatures throughout the oven
5. Out-gassing of some components
6. Melted components, such as some types of connectors and damaged speakers
It is a risk, but many of these risks are evident when you hand solder boards.
Even so, I have one of these ovens and am tempted by buy a PID controller and try it out. Better than putting the oven out on the nature strip.