Reasons why you should consider not getting a tilt shift lens:
1. It must be used with a tripod. Many interior locations will not allow you to use a tripod.
(When I lived in the UK no National Trust locations etc. I remember would allow a tripod indoors, and many did not allow indoor photography at all)
2. Even if you are good at using the lens, a tiltshift lens requires time for set-up, which you probably won't have when shooting on locations mentioned above.
3. Tilt shift lenses have a fixed focal length and are not as versatile fast wide to medium zooms.
4. Unless you use tilt shift lenses a lot, they are not worth getting because of their limited application.
5. Distortion can be corrected using Lightroom or Photoshop software.
6. The "toy" effect can be achieved using software like tiltshiftmaker.com, etc.
I shoot architectural interiors frequently and use 14-24mm f/2.8 and 24-70mm f/2.8 lenses, and a full frame camera that does well at high iso settings. I use them both tripod mounted and hand held depending on location. I posted two of my recent assignments on PBase.
http://www.pbase.com/amoxtli/interiorsI don't want to discourage you completely. You may want to consider renting a tilt shift lens, to see how you like it. Also interestingly, Canon recently released this lens:
http://www.usa.canon.com/cusa/consumer/products/cameras/ef_lens_lineup/ts_e_17mm_f_4lBest of luck. Regards, Walter