Your talk was well presented and provided more than enough information for most developers to get started with profiling their own code. It covered a number of options and extolled the benefits of each well.
I, personally, would like to see some more pitfalls of setting up your profiling (like the ungodly amount of disk space Xdebug can quickly consume if you don't configure it to only run on demand or clear out your old results regularly) and more on how best to focus your time performing optimizations (working out where optimization will have the most impact).
If you're feeling confident enough a demonstration of live debugging with breakpoints would give developers a clear indication of the value of profiling. Maybe even a live demo of finding an intentionally bottleneck in your code as an example of how profiling helps identify bottlenecks quickly.
It was pretty good for a first timer!
The slides were good, Dennis posture was good throughout the presentation and the dictation was also good.
Dennis clearly knew what he was talking about.
On the down side, I could notice he was a bit nervous, which is normal but can be improved by doing more talks and finding ways to release that stress. If we look at other talks, I would say 95% of the talks start with joke(s) and/or some exposure on a personal level like "When I was coming here this and this happened...". This kind of start helps create empathy with the audience which in turn helps the talker release stress, feel more confident and comfortable.
I also felt the presentation lacked some more use cases, some more in depth usage examples. I find this more serious than being nervous.
Nevertheless I think Dennis is just starting his path with Linko and has a nice list of ideas for the future, specially the integration with Codeception, and I am really eager to see how his work with Linko evolves in another talk in the future.
I liked the topic and the presentation. As I discussed yesterday, I'd try to make the talk more use-case driven. Give it a firmer story line to pin the information on. People remember information but they can relate to stories which greatly helps our brain to remember it even better. Looking forward to see this talk and you as a speaker mature. Very good job as a first time speaker.