I bought a ZI back in April. I used it and loved it for months. An M2 was my second camera, which is a great camera. In the back of my mind I always longed for an MP, though, but never thought I could afford it. However, recently I started to really get the itch for an MP. I did a little research and realized that if I sold off the ZI (or the M2) plus my 25/2.8 ZM (which I rarely used as I'm not necessarily a super-wide guy) I could afford a used MP. I ended up finding a very nice MP at a great price, and the seller is going to help me honor the warranty for the next four years. I ended up selling the ZI, mainly cause I got no interested in the M2 and I really wanted the MP. The ZI was a great camera, but I had that itch to get the Leica, despite being such a nice camera, I sorta felt like I was 'settling' I guess.
The finder of the ZI is incredible, but the MP is no slouch, either. However, IMO the feel of the ZI just doesn't compare to the MP, which is hands down, the nicest camera I've ever handled.
Here's the main thing to remember which I realized through all of this. I know I'm not the first person to ever figure this out, but I'll say it again: If you can, get what you really want first. It will save a lot of time, effort, and money. I lost a lot of money buying a new ZI and then selling it a few months later and buying the MP, but I'm OK with that, since I've wanted one from the beginning. I think that now I can honestly say that this is the last main camera I'll ever want to buy. I might be tempted to do something like get an M3, because its a classic, but beyond something like that, there's nowhere for me to go.
I was awake for 32 hours straight. I finally got about 2 and a half hours of sleep and just woke up. If my thoughts are scattered and all over the place, then that's the reason. 🙂