If you're the least bit tech saavy then the Reef Angel is in my opinion the best controller out there. If your not tech saavy though I wouldn't recommend one (as in you hate computers and find them a pain to do anything on). The abilities/options are nearly endless with the Reef Angel, whatever you can think of for a reef tank, you can make it do, just some things require more programming and maybe some additional (cheap) hardware addons. If you are going to buy a RA controller today though, make sure you get the "Mega" version that Roberto just released, big upgrade going from 32k of memory to work with (which I found very limiting when you want to add a lot of custom features) to 256k. Now that there is more memory to work with there will be even more options opened up to do more crazy things with the controller that no one else is doing (like being the first to release an RF module to control Radion lights and Vortech powerheads and give you more features than they have by themselves, ie. custom flow abilities with the vortechs).
I bought mine in 2010 when I was having so many issues with Digital Aquatics (no support, buggy as hell controller that they refused to release a firmware fix for). I told myself then I would never be left at the mercy of someone else when it comes to having full control over my reef controller. It is so critical that it works as planned, which my RK2 certainly did not. Every power port would randomly stick on at different times, and that is terrible when you have heaters on it, woke up many times to my chiller running all night because of the controller sticking. I am sure controllers today are better than the ReefKeeper 2 I was using, but you are still at the mercy of the Mfg to release fixes/upgrades where as with the reef angel you can do them yourself if you have the knowledge, or you can ask on their forum and 99% of the time if it is a reasonable request someone will write the code for you in a day or 2, it is a super friendly and helpful forum with some amazingly talented people helping out.