Essemmlee,
Haven't shot with the 12--but I can say the 15 does a great job for wide shots on the M8. Infinity starts at about 6 feet even at f/4.5.
Here's my CV15 gallery if you want to see some additional samples:
CV15 - a set on Flickr
It isn't "Leica" glass for sure, but it doesn't suck, either. And for the price, its *tiny* size, and its ability to transform the M8 into a "snappy" camera (auto exposure + no focusing = point and shoot capability) is great. It opens up some relaxed shooting possibilities.
Good luck with your selection,
Will