Hi Mark
I have the G7 Canon housing and the Ike as well. I hv just this week received a G9 and G9 Ike.
G7 Canon Housing
+++ used for over 100 dives. Small-> easy for water entry.. wun need tender to pass it to u.. and can do a -ve descend easy!
+++ Ergonomically more comfortable as I have small hands and can do pic/video everything w one hand.. so much for my buoyancy control!
--- worry as it fogs up when water temp too cold
--- o-ring kindda thin.. so I'm always worrying (my old Canon housing for IXUS had a slow leak from front port dat cant be repaired.. so i always worry!)
--- cant move the dial from the housing.. need to press the shortcut button then left right.. cumbersome
G7 Ike Housing
+++ feels solid and does not fog up. o-ring is thicker.. I feel safer.. 
+++ stable for videography
--- my fingers gets kindda crampy as I hv to try to be gentle to half press to focus.. mus hold w 2 hands even tho kindda weightless in water cos I'm not strong
--- MUST carry strobe or the pics wun be good... unless u doing video.. think I might put magic filters for my new G9
--- high set-up cost... for strobe etc..
If only as a no.2 for easy fuss-free dives guess the Canon housing is ok. But from wat i gather.. the Canon housing tend to KO on u when u dun use it often enough.. the o-ring gets kindda 'porous' and the ports get 'leaky'... 
I'm set to go w the G7 n G9 next week for resort diving plus LOB.... I'll come back and tell ya more!..
I'm not so keen abt the WA n Tele.. the barrel distortion is too much and end of the day its no diff for me to carry extra stuffs...

mm