I am not so sure nor "sold" on the 2 handed / spey rod thing yet. I have plenty of room for back cast's on the stream I would use the spey most. I think there are certain things in regards to swinging a single handed may do better.
Some other pro's of the single hander
-feel of the fight
-short casts/swings in slots
-lightweight (I know........a spey is supposed to be easier on your shoulded........they still feel heavy to me and a single hand don't wear me out to much with a good 1 piece smooth casting SA Mastery type 5 or 3, 12' tip. I use to make my own tips.............went back to the factory one piece........hate loops.....all of them)
I may get one some day.........but, it is certainly specialized. I could see it on really big water say 1500 - 2000 cfs or all day long casts with shooting heads(which I don't enjoy no mater what anyways)
- feel of the take if light