Terminating Cat5e and Cat6 is pretty easy with the right tool (I've done it quite a few times) and the results are reliable. I do prefer connectors with some protection (cap or side guards) for the locking clip, and at least with the crimping tool we have at work that's harder to obtain.
I took on the task of running some CAT5e cables in my home about a year ago.
On one hand, it is fairly easy to do, but you do have to have the right tool.
Some of the really cheap crimpers are not very good.
I thought I could just buy the cheapest one I could find, and it would be fine for a 1-day job, and maybe use it far a few cables in the future.
It was very hard to work with, but I ended up just buying a better one, and it was much better.
Still at the same, you have to figure how much does a decent tool, plus all the connectors and a box of wire all cost.
Most people will be better off just buying premade cables since they are very cheap.
I got into the DIY because my brother-in-law works for a telecommunications company and gave me the wire and connectors for free.