How do I feel about last year's decision to go all T lenses on the T? I do miss the M lenses. They are tiny, intricate, amazing works of art. But I do not miss using them on the T (having gotten to try out a SL with an M lens in Los Angeles last year, that camera is an amazing platform for using a manual focus lens: huge integral viewfinder and focus assist. The T has neither).
I have been really happy with the native T lenses. I am really excited about the upcoming primes. A large part of the appeal of the T is its aesthetic, and the T lenses maintain that aesthetic.
The 23mm is probably my most used since it makes the camera as small as possible. The 18-56mm is a great lens in terms of versatility and quality. The T wide angle and telephone zooms are really great as well. The 11-23mm, though used infrequently, may be one of my favorite lenses ever. And the firmware upgrades have made the T plenty fast and responsive.
As I have become a Leica-focused shooter over the past five years, I have also tended to value depth of field over subject isolation in my photos. Right now if you want a lens that opens wider than 2.0, you need to go with a non-T lens or wait until the 35mm T lens coming out in the near future.
If the T had focus assist (focus peak, etc.), I would be more inclined to use manual lenses with it. That being said, if you enjoy manual lenses, the fact that you can use them is a bonus.
The T is about achieving flexibility while maintaining usability (this is very difficult, as per the Flexibility-Usability principle). Keep the amount of functionality to an allowable minimum while giving the user the option to use as many different lenses as possible.
If I wanted to have M quality glass and M quality output (and not buy an M), I would buy the Q, and live within the flexibility limitations, which I have done. How often do I use manual focus on the Q, which is probably the digital non-rangefinder Leica most suitable for manual focus? Pretty much never. Hence I will stick to the T lenses on the T.
The Leica T remains the system camera that I have always wanted.