I've been using an ikelite SLR housing, for about 8 or 9 years. And now have added to it, the ikelite housing for the canon G2. Never had any problem at all - no leaks or doubts - because the housing and ports being made of clear lexan, you can see the o-rings seating, even after clamping.
An inspection of this, during and after assembly, and you know that the seals are not pinched, or extruding some direction or other...
In short, I can't imagine why anyone would pay 2-3 or more times the price of an Ikelite, if the Ikelite is available. In almost all ways, the ikelite is superior.
The Ikelite, can support full camera strobe TTL automation. So at least you have the *choice* of using strobe in auto for macro, or wherever TTL just works...
I mean, saying, "Just learn to shoot manual", is all very well, and is not, actually that hard a thing to learn. But I hear it more and more from folks who have just purchased a manual only housing.... 
It seems to me, that spending 2-3 times the cost of an ikelite, for a non-transparent housing, which *prevents the option* of using auto strobe, and prevents seeing the o-rings after latching closed, just doesn't make any sense....
Just my own opinion.
And the question about the OLY pt-010 as the first, because cheapest, digital housing to buy - this may be fine, if you can live with the depth limit. I like to go to 130-150 feet pretty regularly, and so I knew I couldn't use the oly.
Don