I'm currently going through MotB with my chaotic neutral swashy/fighter/duelist from the OC, and I've concluded that the spirit meter is probably most cumbersome for neutral characters. The only really viable options seem to be lawful good and chaotic evil. It's quite difficult managing the spirit meter with a craving of 3 or 4 whilst only devouring 2/3 spirits per day, since the meter is always filled up to somewhere in the middle, so you always have to keep an eye out for it, especially when traveling. It actually made me give up trying to remain neutral, so I just started devouring everything in my path. Now it isn't cumbersome at all. It's even quite cool from a roleplaying perspective to succumb to the selfish evil path as a result of being cursed. Also, One Of Many makes it all worth it; he's so kickass as a warlock.
I must say that I'm truly enjoying MotB. I had a hard time early on because I tried to tackle Myrkul's Vault too soon, but once I did the other quests it got a lot better. 7 levels of weapon master really helped too. I thought the OC was okay, but too linear and too Disney. Somehow having to save the world always makes me feel guilty for choosing the evil options, but in MotB I have no such remorse at all. That must be because of the more personal storyline, and the fact that there's no overdose of whiney good companions.