After my Sigma 17-70mm bit the dust (I think just finally wore it out -- I used it almost every day for 2.5 years), I decided it was time to replace it with an even wider model. Although the 17mm was great for architecture outside and pretty good for interiors, it was still not wide enough for tight interior spaces.
Needless to say, with this new 10mm lens, tight spaces are no longer a problem! I am amazed at how much more I can capture with the extra field of view.
Highly recommended for interior architectural photography.