After a long time of debating with myself while tracking prices for this season pass, I finally decided to bite the bullet and trust cdkeys.com with my money since they've always had the cheapest price for it. This was my first purchase on the website and I can honestly say that the whole experience felt incredibly professional every step of the way.
Once the Paypal payment was complete and I had received two confirmation e-mails for my order (one from Paypal, the other from cdkeys.com), all I had to do to access my newly-purchased Steam key was perform a 2-second phone number verification via text. After I typed in the four-digit code I had received on my phone on cdkeys.com, I could access the key straight away and there were no problems adding it to my Steam library.
Based on this initial experience, it is safe to say that I will be using cdkeys.com a lot more from now on. Great job, guys, you really deserve all the praise! ;)