Size compared to the Minolta 58mm f1.2.
Although the X250 does not focus as close as the Tamron mirror lenses, it's still pretty good at minimum focus distance of 2.5 meters. You can get pretty good close ups. The original hood the came with the lens is way too short. Mirror lenses tend to flare more easily than all glass lenses. A longer hood would have helped to reduce the flare problem.
Bright Lights -- NEX-5N & Minolta RF 250mm f5.6 on tripod.
In think in terms of image quality, it's probably as good as a consumer lens would get for mirror lenses. The build quality is excellent with very smooth focus action. It's a perfect lens for EVIL cameras. The longer focal length allows some stealth pictures to be taken without people getting mad at you, or, simply, some like the compressed perspective of long lenses.
Talk -- NEX-5N & Minolta RF 250mm f5.6