I use this style and I got pretty good with it before I stopped playing competitively like half a year ago. I was rank 900 at the top of my game and Aevv was an amazing player who used this style. That guy could stream anything. It's possible to get really good with it, just look at PeaChick. However, you'll notice he HD-HRs a lot of stuff, and I can personally say that the reason is that playing this style seriously limits your ability to aim accurately with your mouse at high clicking speeds. You'll have amazing aim and accuracy at lower speeds, which can make HR kind of easy after a while of practicing it, but if you start doing high speed DTs, then you'll start having issues. The reason is that you can't really stabilize your mouse too well while clicking one key on it. Furthermore, alternating is extremely difficult when you have to switch between hands, so you'll find yourself doing a lot of single clicking whenever you don't stream, which exacerbates the problem. Another issue is that slow streams can be very difficult with this style. The explanation for that is a little hard to verbalize. Basically click/x players tend to treat their streaming like pressing both keys at the same time one slightly behind the other, so it's less like alternating your hands and more like clicking with both hands at the same time over and over again... like (m1k1-m1k1-m1k1) instead of (m1-k1-m1-k1-m1-k1). That's why fast streams are easier this way and it is also why timing a slow stream accurately takes lots of practice and highly spaced streams can take practice too. Get ready to develop some serious forearm muscles.
I actually wrote an article on how to get good playing this style just before I quit competitive play. Some day I might release it. I guess I didn't post it simply because I didn't feel like I was good enough to be publishing advice, so to speak. I do think I am something of an expert on this style, however, since it's all I played for the year and a half or more that I played this game.
Anyway, hope that helps. Cheers.