My current weapons are a Sony A100 DSLR and a Sony HDR-CX130 DV camera. The lenses I have are a Sony 18-70 which came with the SLR, Minolta 35-100 and Tokina 100-300. The latter two lenses were used on my mother's old Minolta film SLR, and when my parents decided to go digital, Sony was the only real option for them because of the lens compatability.
I'm now thinking about upgrading my SLR if the tax man is kind to me (and considering he owes me almost enough for a new camera from last year, it should be good!). Again for the lens compatibility, I'm probably likely to stick to Sony. I've been looking at the A57, possibly with the 18-55 and 75-200 twin lens kit. If I was entering the market fresh I'd almost certainly go with a Canon, but I want to be able to continue using the equipment I've got and mix it up occasionally.
Anyway, any thoughts from any other Sony owners? or particularly anyone who has used Sony alongside other cameras
I had a Sony A100 which I used alongside Canon digital SLRs.
In the case of the A100 I compared it with the Canon 400D which had the same resolution (10Mp).
I went to a lot of trouble to take as nearly identical photos as possible with a range of lenses and I found that the A100 had inferior colour and a reduced dynamic range, at least using JPEGs out of the camera.
I had managed to pick up a Tamron 28-200 XR series in a Sony mount second hand for $135 and the combination of that with the A100 gave me amazing flexibility and really sharp photos, the Sony couldn't cope in challenging light conditions compared to the 400D.
So I bought a Tamron 18-250 for the 400D (for about $650) and gave the A100 and the four lenses to my cousin who was using Sony for her work as a professional photographer. The Tamron 28-200 is the usual lens on her full frame A900 now.
My cousin now has an A55 which I've used occasionally but I'm not sure I like the electronic viewfinder but she likes it.
I think some of the advantage the Canon had was due to using CMOS rather than CCD in the A100, and the later SLTs have CMOS now. One thing that had annoyed me about Canon was inconsistent auto white balance in daylight, which I overcame by using pre-selected white balance. Cloudy WB is a big help on dull days.
However, the Sony, even the A57 is quite expensive and you could get a Canon 550D for less money.
In case you can't guess, I'd recommend getting a Tamron 18-270 zoom with whatever body you end up with and, as a result your existing lenses would not be so important.