The problem is that Sony already has some good entry-level and mid level cameras out at the moment, and also on the full frame end...the bias against them doesn't really seem likely to go away. There are many layers of complexity to it...
1. Canon and Nikon are massively established, and will maintain that perch for quite a while - Sony, Pentax, and Olympus will all have to routinely struggle to be noticed behind the shadow of those two, no matter how good their products are. Take a look at any 'DSLR questions' type of forum where beginners ask for advice on what to buy - 90% of the threads on virtually any boards will mention Canon, Nikon, or a choice between Canon or Nikon - without even a mention of other brands.
2. There is some bias against Sony - many folks just hate the corporation from other ends of their business, and carry the dislike to their cameras. Don't like PSP, don't like rootkits, don't like BluRay, don't like Memorysticks, etc - then automatically, many of these people are more than willing to perpetuate bad word of mouth about Sony cameras despite never having actually handled them and against photographic evidence to the contrary.
3. Sony shoots itself in the foot all the time. Where is the marketing for the new cameras? How will people know the A500/550 exist if there are no TV ads, no massive internet ads, no big magazine spreads, and due to your stringent SURE sales practices, no cameras on the shelves of many stores? The cameras may be (and are) fantastic, but you need to let people know they exist, and know what makes them so unique and such a great choice for many folks, from beginners to pros. Nowhere has Sony advertised or pushed their wholly unique live view system which should be a major selling point...or the 5/7fps shooting speed, or low light focus capability, or built-in HDR, or high ISO ability.
4. Sony doesn't have to aim for #1 - being a solid #3 is not a bad plan, and eventually once established could earn you respect that comes from longevity and solidity, and maybe #3 eventually moves into #2. Either way, keeping at it, not making too many drastic changes to the line, keeping downward compatibility, maybe consider a few more firmware updates to show commitment to current owners, etc would all help slowly disintegrate the bias against them, the occasional bad will from their own disillusioned users, and the general unconscious bias from virtually all camera testers and media sites against the Sony products which tends to overly highlight missing features or shortcomings that receive a pass on other cameras by the 'big two'...or failing to acknowledge a unique Sony feature that should receive mention in reviews of other cameras as 'missing features' or 'cons', but don't.
Just a few observations. In the end, the A500/550 are indeed excellent cameras that would be fine choices for many beginners, as well as a fair number of very skilled and experienced photographers...and they are every bit as good as their competition overall - missing a feature or two, but also with some unique features missing on the competition. There aren't any bad DSLRs out there - so whether the A550 is right for someone is up to how it feels in your hand, if it has the features you want, and if the price is right. It certainly was for me.
Sony DSLR-A580 / Sony 18-250mm / Minolta 50mm F1.7 / Sigma 30mm F1.4 / Tamron 10-24mm / Tamron 150-600mm / Tamron 90mm F2.8 macro / Minolta 300mm F4 APO
Sony A6000 / 18-55mm F3.5-5.6 / 55-210mm F4-6.3 / 10-18mm F4 / 35mm F1.8 / 16mm F2.8 / via manual adapter, lots of Pentax K mount, Konica K/AR mount, and Leica M mount manual lenses