in that situation? Since you're new to SLRs, you don't have to worry about having a lot of legacy lenses, so the field is open.
Nikon is pretty well known for being the "king" of low light, though some of the newer Canon's are supposed to be challenging that.
That said, it's not entirely accurate to say that the Olympus is not a good low light camera. It can be a fine low-light camera. The four thirds sensor in the Olympus cameras is smaller than the APS and FF sensors in the cameras of other brands. This can cause some more noise at higher ISOs, but in many cases, none of the noise is obvious unless you engage in pixel peeping. And that's SOOC, if you shoot RAW (or even edit your JPEGs), you have all sorts of options for handling the noise. The newer Oly's have supposedly closed the gap significantly (with the E-30, and E-620 for example).
So granted, there are some high ISO issues, but there are also benefits with the 4/3 sensors (Olympus, Panasonic and Leica use 4/3) - it's exactly 1/2 the size of a 35mm (film) sensor. What this means is that you get a 2x equiv with your lenses. A 70-300mm is actually equivalent to a 140-600mm 35mm lens. Since the sensor is smaller, the lenses can also be made smaller. All of the 4/3 lenses are made specifically for digital, rather than being reworked film lenses. Another advantage is in-body Image Stabilization. You buy it once, with the camera body, instead of each time you buy a lens (the IS also works great with legacy 35mm lenses - you can get adapters for almost any camera's lenses for about $20, and find great buys on eBay and in pawn shops on old glass). Oly is pretty good at innovations, for example, dSLR Live View and Sensor Cleaning originated with them.
Also, don't forget to look into Sony (previously Konica & Minolta, which merged and then the technology went to Sony), and Pentax - even Sigma, a company mostly known as a third party lens manufacturer, now sells a dSLR. You might also want to look into the new breed of micro 4/3 cameras like the Olympus E-P1 (Pen) and Panasonic GH-1 - they're basically dSLRs, but without an Optical Viewfinder and a mirror - quite compact.
Anyway, wonderful photos - I think you'd really enjoy a jump to a dSLR.
Edit: Here are some Low Light/High ISO Oly photos:
http://www.flickr.com/search/groups/?q=high%20iso&w=10349025%40N00&m=pool