There are no reasons to steer clear of Ikelite. It is a good product.
No doubt that the more expensive alu-housings are better, but are they worth the extra money? Only you can answer that question and it depends on how deep your pockets are and if you are prepared to sacrifice other things in life to have an alu-housing instead of a plastic one.
I realize I am a bit late to this thread but I wanted to point out a concept that I rarely see mentioned in this forum, what you might call the "technology cycle cost multiplier." In the olden days of film cameras, we often kept the same camera bodies and housings for many years (I had a canon F1 with speedfinder in an Ike housing for roughly 15 years). These days, we all fall in love with the latest improvements in digital SLRs, if not pixel counts, then better autofocus, HD video, whatever. SO, this leads to a short product life cycle. So, when you invest in that beautiful Subal, Seacam or even less $$ aluminum housing, think of how often you'll want to replace it down the road. In the last few years I have gone from a Canon 10D to 20D to 40D and now I'm eyeing the 7D. That's a lot of hounsings and when you multiply the price difference between Ikelite and the next most expensive housing, that's a lot of cash. I know a number of Subal and Seacam owners of somewhat outdated camera bodies who groan out loud every time a new canon or nikon SLR hits the news.
So, I'll stick with Ikelite. But, I should mention an important negative of Ikelite housings. The viewfinders are really poor, IMHO. I purchased a nice Dyron 45 angle enlarged finder that fixes this problem fine for me (and I'll just move it along to that 7D housing when I decide to buy it).
Mike