Is the Rebel T1i an upgrade or downgrade (from 20D)?

It's a much better imaging computer than the 20D. Far more modern and a better sensor yes. It's a lot smaller and lacks the QCD of the XXD cameras. That being said, I've never used this newest dReb.

What ever you do I would not spend $378 to repair a 20D. You can pick up a used 30D for about the same price or get a used 40D for around $650.
The New Rebel does look pretty impressive and so far I have heard its very good. For me I would weigh what is most important the stronger body and faster frame rate of the XXD or the video and smaller size of the rebel. Obviously there are many more factors that come into play but that is what made me stick with my 40D. Both are very capable of taking better photos then your 20D.

I've never had a 20D but recently acquired the t1i. Is it an upgrade from the 20D? Does the 20D have the t1i's features? 15mp, self cleaning sensor, hd video, huge lcd monitor that's easy to read. I think the newer technology makes it an upgrade in many respects.

It's a big upgrade.

And that's coming from a 20D I used constantly for 4 years shooting on the street and then last year choosing the XSi (over the 40D). The XSi is now being replaced by the T1i, which has an even better LCD display and a little better resolution.

The much larger LCD that both the T1i and XSi have over the 20D is just as important for usability as is the bump up in image quality from the newer cams. The larger LCD is great for being able to see the camera's shooting parameters clearly. Tons better than the top LCD on my 20D cam. And of course the bigger LCD is better for reviewing images as well.

Thank you for your answers Ken, Tommy, and Len! I have a few other questions now:
40D doesn't work with EF-S lenses right?
I'm liking the rebel ~ very interesting that is has video capabilities that is a fun feature, but more something I would want from a pocket sized point and shoot. Does the video have sound too? I love the large screen view and that it will be lighter than my 20d.
About the image crop: is there going to be a noticeable difference? And does the rebel have raw shooting mode?

Thanks Brad! Your screen comparison was really helpful to me. LCD size is so nice and bright. I'm going to see this in person too The picture they have of it on the canon site is great! Do you notice any difference of the image cropping? 20D works really well for wide screen ~ the rebel does too?

No, the 40D DOES WORK with EF-S lenses. As does the 50D and all of the current and recent xxD bodies.

The "Rebel/xxxD" series and the xxD series (with, I think, the exception of the now-ancient 10D) are the only cameras that take the EF-S series and they are all roughly 15x22+mm sensors (=APS-C).

The 24x36mm (=35mm film size) xD cameras, however such as the 5D and up, will only take EF lenses.

If you could stretch to a used 40D, that model represents a real upgrade to the 20D and shares the control system that you are already accustomed to. The 30D has improvements, but I'm not sure I'd pay a lot more for one than for a used 20D.

If money is tight, and when isn't it?, you could do a lot worse than either a used 20D or 30D. After all, your broken 20D was a used camera (by you) too, wasn't it? Most of them on the market are probably because of wanting more pixels etc, rather than something wrong with the camera.

And yes -- a HUGE thumbs-up on a 40D should you decide to go that route.

Yes you can use EF-S lenses on the 30/40/50D or any rebel body. I too would suggest either a 40D or a T1i. Both are significant upgrades from the 20D.