Ask HN: Your most awesome experience (UI/computation/language...)?

Here are three examples of what I call awesome experiences and while they are a little dated, I still cherish them. They are also very easy recalls as I can say exactly what changed at the moment I first used these models/processes:<p>* Back in the days, I used to write most of my graudate research with Fortran generated results... the process was excruciating. Then one day, I discovered Matlab quite by accident (Matlab was not part of our domain limited culture) and I never looked back, thereby becoming an evangelist on the matter with other grad students. The ah-ah moment came when I could produce in 15 seconds and 3 lines of code a graph that would have taken me much longer in Fortran. The example is simple but for the first time, I also discovered that a language could be an impediment in my thought process and got me interested in listening in on the LL1 and LL2 conferences.<p>* Some other times, the revelation is seamless. The UI for a search engine like Google really puts the search at the center of the user's concern. It's not about ads (well not in the first screen), it's not about building portals and categories (which presumes that you think in terms of category first), it's about a sober interface centered on the user and a capable algorithm. The HN login session also falls in that category.<p>* Another example is the pay-as-you-go payment process with Skype. For the first time, I was not paying for a monthly payment for my phone bill. The pay process, even if more expensive sometimes, is worth a lot to me and I now always evaluate payment models with this one in mind.<p>Do you have any other similar awesome experiences that swiftly became your gold standard for future interactions ?