Congrats on the new purchase - I was going to come in here and advise, but you've come to a decision already.
I would point out, just so you don't experience any disappointments, that the A550 really isn't an A700 replacement. I think that was the root of some long, nasty debates on other forums that ended up getting the A550 some stupid and mean word-of-mouth.
The A700 has a more 'pro' interface, and a few features that either extreme pros or folks who take very specific types of photos might value - the dual control wheels, the direct access menu, weather sealing, MLU, DOF preview, and AE toggle. This doesn't mean better or worse than A550, just that it is built with a slightly different intent and generally marketed to semi-pro to pro photogs (even if many of the users aren't).
That said, the A550 has its own slate of features which the A700 doesn't have, that some may find valuable or even crucial in a new camera - HDR mode, live view, manual focus main-sensor live view, and tiltable LCD.
My own personal experience with the A550, which I've owned since the beginning of November, has been excellent. The build quality is very good - no flex, squeaks, etc. The focus speed is excellent - super fast and accurate. The ergonomics work perfectly for me - excellent grip, AE-L button where it should be, Fn menu very well laid out for fast settings changes, dedicated ISO, DRO, drive mode buttons. Burst shooting is shocking if you're not used to it - 5fps tracks beautifully in AF-C mode and is very fast, and the sped-up 7fps mode is pure machine gun. IQ is great in good light, and even better in low light...high ISO performance extremely good - noise is very small and uniform, mostly lumi with very little chroma, and NR works effectively on in-camera JPEGs. I personally use up to ISO6400 regularly and with confidence...ISO12800 in a pinch for emergencies. Battery life is forever. White balance is very good and accurate. Metering is reliable - seems to lean towards a slight overexposure, meaning dialing in -1/3 or so gives perfect metering. DRO advanced mode is excellent with dynamic range in challenging light, and HDR mode is even better...not only in increasing dynamic range in shadows with no noise, but also for reducing noise and increasing detail at high ISOs by stacking two frames (not an advertised function, but works a charm!).
Hopefully your experience will be as good as mine - look forward to seeing how you do with the new cam. Don't think of it as an A700 replacement though - think of it as an advanced entry-level/ entry-enthusiast cam with some seriously trick toys and nice standard features.