I've also been a paid user of Alfred for nearly a decade. I tried Raycast in it's early stages, also became a paid user, and haven't gone back to Alfred.
I adore and appreciate Alfred, it was one of the first applications I would install on a new Mac. However, Raycast is a very well polished product and has been a great add-on to the daily arsenal.
It being closed source doesn't mean that they are any less trustworthy or competent. Trust me, I am totally on board with what you're saying. In this case though, I'd say there would be no need for concern. The developer behind BTT and BST has established trust with their users, great communication and good support.
Also, as for BetterTouchTool being able to replace Karabiner, I have to disagree. I have used both for as long as I can remember and consider them "must haves." But for me at least, they have always been separate in their use and function.
I made the unfortunate mistake of upgrading to Sierra before doing a more thorough check of all my application's compatibility with Sierra. I found out about Karabiner too late - total bummer. I hope an update rolls out soon. (I haven't tried the current "interim" application they created - I need the real thing)
I've searched high and low, all over the place for a bookmarking service that satisfies and works well. I've even thought of developing my own, or improving a now defunct service. However, I've recently started using Pinboard. So far, it's certainly the best I've come across. It allows for good organization, takes away the "social" aspect of many of the other bookmarking services - I'm not really looking for my bookmarks to be "your" bookmarks.
My biggest issue was finding something that would allow me to begin to approach the task of organizing the some ~7,000 bookmarks I already had hoarded over my numerous browsers. Pinboard has at least allowed me to begin the daunting task. I'll see where it takes me.
Ruby (and certainly Rails) is still very much in-demand, and I'd say is still "trending" in terms of development languages. Granted, Ruby (Rails) tends to get lost in the sauce with the continual uprising of new languages and frameworks catered towards web development. However, I think that Ruby's strong community, even more-so with the Rails community, is what would make it such a good language to learn for the job market.
Aside from Rails, I think that Ruby will see even more of a surge in popularity with the recent progress in RubyMotion (they changed their pricing plans, and the platform is more easily available to the average developer now). I'm only now dipping into RubyMotion, but it's wonderful if you want to develop on the iOS or OSX platforms without getting heavily involved in learning Objective-C.
Anyways, I'm getting off-topic. Point is, I think Ruby is a very good choice. Being that Rails is the most popular framework in Ruby, Rails would be a wise choice to become familiar with too.
I adore and appreciate Alfred, it was one of the first applications I would install on a new Mac. However, Raycast is a very well polished product and has been a great add-on to the daily arsenal.