I think a lot of people are concerned, on the strength side, with the lateral forces that might be applied to a cartridge bearing.
For sure, most cartridge bearings for bicycles are designed for other applications, mainly in electrical motors, but also in a range of industrial applications. In these cases, the lateral forces might seem to be minimal... but are they really? Does a ceiling fan have no lateral force when the blades are acting like propellors and trying to whizz the shaft into or out of the housing? Does the act of tightening a fan belt on a car mean there are no lateral forces on the bearings in the alternator, or are there quite strong forces trying to turn the shaft sideways? There probably aren't meant to be these lateral forces, but I can guarantee there will be, even with things like thrust washers in place in the shaft.
On a bicycle, I don't think the lateral forces, even under a loaded touring bike are going to worry a pair of properly installed cartridge bearings. Certainly experience shows otherwise, with perhaps the most-used example on my bikes being the bearings in my SON Dynohub.
For my part, I love the fact that sealed bearings run so smoothly right out of the box. A case in point:
I have bought a few sealed bearing hubs in recent times. A Velocity fixed-gear hub, a Magura front disc hub and a pair of Novatec hubs. They all obviously vary in the bling and quality factors, but one thing about
all of them is that they spun perfectly right from unpacking.
I bought a pair of Velocity Dyad wheels with the Velocity c&c hubs. The rear was just OK in how it spun. The front was a complete disaster with way too much preload. Now this is an Australian company that has a worldwide reputation for quality. The front hub preload was a stinker. The wheels were returned to Velocity anyway because they were the wrong hole number (32 cf 36). I'm hoping the replacements are better, otherwise I will have to rebuild them myself.
Machka's bike had Formula sealed hubs. When the rear one got really noisy and clunky, I dismantled it. The operation itself is no worse than undoing a c&c hub, and in fact is better if there are loose balls in the c&c version that will spill everywhere. Her bike has been to hell and back... several times... and when I peeked under the seals of the old bearings, they were relatively fine. The problem was more to do with the friction fit of the bearings into the hub housing, which I suppose is an issue that balances out any disadvantage of c&c hubs. Fitting the new bearings was a complete cinch... with the right size tube for the inner race, a bench vice and a few taps of the hammer.
As to the issues of water ingress and seal lubrication as indicated in the supplied link above... well, I don't have much time for Mr Brandt's opinions on several things. What I do understand is that SON had problems with the initial batch of their dynohubs, with water penetration through the seals. Certainly, the fix has been a good one with my hub coming up to around 40,000km of service. I think the official strip-down service interval for these hubs is around 50,000km.
It's also important to remember that cartridge bearings can be sealed, unsealed, or sealed on only one side. There is a whole array of bearings that have been adapted by bicycle component manufacturers/designers. I discovered this link the other day just to show this:
http://www.diymtb.com.au/static/EnduroBearingList.asp
This one contains some information on standards and abbreviations -- and take note of where Shimano and Campagnolo's ball bearing quality actually falls in the world of bearings:
http://www.diymtb.com.au/static/enduroBearings.asp
It's an Australian site. But when I did the rebuild on Machka's Formula hubs in Canada, I got the parts number from the side of the bearing and trotted off to a nearby industrial bearing supplier. "Yeah, we've got that one in stock".
Sheldon Brown has basically said on another thread in Bicycle Mechanics that Shimano hubs are better than any other hubs on the market except Phil. I'm still testing his opinion. But I do wonder if a Deore hub will spin happily in all sorts of nasty conditions for 50,000km before having a scheduled rebuild?