I wanted the Rebel t1i (eos 55d) for a while, but now the Rebel T2i (eos 550d) has come out. I got it for the same price as the t1is are selling for here. It has better specifications and way more options for movie mode... mic jack for stereo sound (otherwise you are limited to the low quality internal mic which also picks up all the internal mechanism sounds of the camera), more manual options, more frame rate options.
I'm very happy with it & the photos (& movies) look amazing. But that said, the 500d is still a great camera and if movie mode features are not such a high priority and you can get it cheaper... go for the 500d / rebel t1i.
In my opinion, dpreview.com is the most comprehensive website for reviewing digital cameras, and here's what it says about the rebel t1i:
Conclusion - Pros
* Good resolution and detailed output (but only very marginally better than 450D)
* Decent (but not 'best in class') high ISO JPEG performance
* Extended ISO speed up to 12800 (not great quality but it's there for emergencies)
* Good quality HD video (but sound output does not match the image quality)
* Currently the cheapest 1080P video capable DSLR (albeit only at 20fps)
* Overall snappy and responsive performance
* Very clear, high resolution 3.0 inch screen with anti-reflection coating (but still hardly usable in sunny conditions)
* Brightest and largest viewfinder in class
* Good number of external controls provide quick access to all important shooting parameters and the interactive quick control panel is a good alternative for those who prefer the compact camera style of controls
* Intuitive menu system and customizable 'My Menu'
* Good control over High ISO NR
* Fairly efficient Highlight Tone Priority features preserves some additional highlight detail
* Reliable flash exposure
* Peripheral illumination correction
* Optional battery grip
* HDMI output
* Comprehensive software package included
* Good battery life
Conclusion - Cons
* Visibly more noise in RAW files than some of the competition
* Slightly less highlight range in JPGs than the competition
* Relatively limited RAW headroom, channel clipping means color accuracy can often not be maintained when recovering clipped areas in RAW conversion
* Metering has occasional tendencies to overexpose in very bright, contrasty conditions
* Unreliable auto white balance and presets under artificial light
* Still slightly plasticy appearance and surfaces
* Grip is a little small for larger hands
* Flash has to be raised for AF assist (although AF is good even in low light)
* Limited exposure compensation range (+/- 2.0 EV)
* Contrast detect AF so slow it's useless for most types of photography (it's the same for most of the competition though)
* Slightly more expensive than the competition