Generally speaking, I would like to say the whole journey of ML1 to ML10 has been very rewarding. ML2 and ML3 are really annoying, and I can see a lot of people giving up after the painfully stupid 2.10 or the hell of Temple of Twilight. However, things really improve after that, and I would recommend anyone to devote some time to MLs. It is lots of fun.
For myself, I was only ML4 as late as the previous weekend, got ML5-ML7 during it, and then ML8 and ML9 this past weekend, and ML10 last night.