I've had an mp40 on my 75 gallon (283 liter) for around 3 years now and just replaced my other two pumps (koralias) with an mp10 and I love it. It is very nice to have all the varied speed programs to choose from. I also really like the look of having no cord in the water.
The only downside besides price is that they seem to take around 2 weeks to quite down after you first buy them, but after that its not too loud unless your running it full speed, then it can be heard for a few feet away.
It is really up to you whether the price is worth it. They definitely work well and the only problem I've had in the 3 years with the mp40 was the power supply dying, which was replaced out of warranty by ecotech, free of charge. The company knows that the pumps price is high and in return provides impeccable customer service.