Digital cameras forum: Decision Time: Rebel XTi or Nikon 40Dx

Since your film camera is EOS, the lenses should work with the digital EOS. The difference is that there will be a crop factor with a cropped field of view. So your 28-80mm lens will work like a 45-128mm lens on the XTi, whereas your 75-300mm lens will work like a 120-480 mm lens.

Either the Canon XTi or Nikon D40x are comparable and good entry-level D-SLR. They can shoot up to 3fps, so not terribly fast but fast enough for most. The lenses you have are slow zoom lenses, which will work well in daytime outdoor or well-lit settings, or when flash is used in low light. Digital D-SLR tends to have more motion blurring than film SLR, and so you typically will need faster shutter speed to freeze the action than film SLR. For low light action without flash, I often need to use fast zooms f/2.8 at high ISO. But you can see whether your existing lenses work for your shots, and decide on upgrading your lenses.
If you want to save some money, stick with Canon which is at least as good as the Nikon D40x, perhaps may be even slightly better in terms of high ISO low light performance and better autofocus (XTi has the same autofocus mechanism as the more expansive Canon EOS 30D). But it lacks spot metering and some people complain about lack of ergonomics.
So you should go to a local store and see which one you like better in your hands, then factor in the decision whether you want to buy brand new lenses. Either camera is good, and you won't be disappointed. It will make more economic sense to buy the Canon and keep the current lenses, and spend extra money if needed to upgrade the lenses, rather than spending extra money to buy brand new entry level camera body and entry level lenses. The Nikon kit lenses 18-55 and 55-200mm lenses are slow zoom lenses too, like your current lenses.
You should also consider getting an external flash and a good diffuser like the Gary Fong Lightsphere II (clear is better than the opaque version) if you do a lot of baby portraits. The Gary Fong Lightsphere or his other inverted dome diffusers are the best you can get. Also don't forget a good photo editing program like Photoshop or other equivalent programs. A monitor calibrator like Spyder or Huey can save you a lot of time and frustration especially if you print a lot of photos on your own printers.

I think buying a D-SLR is like buying a computer or laptop. Soon after you think you have bought the latest meanest machine, it became yesterday's lost luster technology. In 1991, the first D-SLR from Kodak was just 1.3 MP and cost $30,000. Then in 2000, the Nikon D1 shock the D-SLR world with a whooping 2.7MP at $5000, taking over the Kodak's domination at that time. In less than a decade, the D1 is now obsolete and some people may even laugh when they hear today that someone has spent $5000 on a 2.7 MP camera. But that is the cruel reality of technology. Things become obsolete fast.
But don't despair, a lot of master piece have been made by cameras with less ability. Camera is just a tool. The photographer is still the composer. You will still enjoy great photos with whichever D-SLR you end up with. Better and more advanced tools just make it easier. Have fun with photography. It is an art more than technology.