I see a lot of feedback in the Windows feedback app, with users complaining about how slow or laggy the Windows 10 TP Build is on their Lumia phones
And while the common reason is because it is a technical preview,but a lot of users still have a hard time understanding what a technical build is.
So allow me to offer a couple of analogies to the situation:
In the automobile industry, when cars are tested for their safety, these cars have no leather seats in them, nor do they have sirius satellite radio, air conditioning, no premier alloy wheels or a navigation system. In fact most of these crash test cars aren't even painted. why? because it doesn't matter, these are the features or functions that are being tested.
Next analogy would be the case of Nascars, these are essentially cars with 3 things, an engine, a pair of seats and a protection frame. you don't need anything else, you have got everything you need right there. Even the whole exterior body of the car is made from cheap metal.
What this all means is that when you are running tests or building something for a specific function, all you need are the main components to make sure your build is tested properly and in the case of Windows 10, that's what Microsoft is doing currently with Windows 10 for Mobile.
The technical previews build for WIndows 10 on Phones is a technical build, so we can look at it, use it from a technical view, and give technical feedback like bug reporting, feature suggestions and more.
These technical builds aren't fine tuned or polished and rightly so. They are just builds for testing!