Sort of. The "sweet spot" is for squeezing mind flays in between mind blast, with all 3 ticks. With MF being a 3 second channel and MB being on a 5.5 second cooldown...
0 rating = 1.2 MF (1 full MF with 2 ticks)
299 rating = 2 MF, 9.09% haste
800 rating = 2.1 MF, 24.4% haste
1640 rating = 2.2 MF, 50% haste
2097 rating = 3 MF, 63.95% haste


The reason there are jumps from 300 to 600 to 800 for "sweet spots" is because theorycrafters try to take into account spell pushback from raidwide damage or new adds or what-have-you, thus taking one tick away. It's all supposed to balance out to a whole number of MFs. If there isn't any pushback, then you're going to have to do what is called "clipping;" basically ending the channeling early and lose one MF tick.

However, it's absurd to try and have and maintain close to 300 or 800 haste without ever stopping at anything inbetween; More haste is always better, regardless of how many ticks you might be losing. It is important to keep in mind that these "sweet spots" were conceived before haste affected our DoTs. Considering that most of our damage is coming from VT and DP now, we can basically skip over the MF sweet spots. More haste is better, and you're bound to hit the irrelevant sweet spots as you gear up to make your DoTs faster.