No. Delegates are for more complicated and hard ware eating compositions.
I read now threw AE´s help file. Seriously... It is easy to understand (well I think so) and you don´t have to read threw everything. I´ve learned quite usefull things.
Did you know that you can set a layer-keyframes with everytime you press * during a RAM Preview? Pretty nice to find the syncable scences faster!
However a delegate example:
This frame takes 20 layers for my complete animation.
http://img161.imageshack.us/img161/1362/01pf1.png
(please click the link, ´cause it´s a fullscreen 328kb png)
There is: fractal noise, blurs, just say: All the stuff that makes AE render for 1 hours (if I want the whole 20 second segment; 3,4Ghz 1GBRAM).
If you work with AE, you know that it often takes a longer time to render one singel frame in the preview window and this takes a lot of time when you´re working and well: It sucks a bit to wait often 5 seconds just for a little change =/
Back to the screenshot. The background could be one single composition. I would render a 160x120 delegate in MJPEG. AE´s seetings now are defined that this small clip is a delegate of the background. I add the background-comp into the whole mix and:
He only uses the delegate for the preview until I tell AE: "Stop using the delegate!"
(good for fast preview files! Takes away a lot of render time when you use delegates)
The wonderful thing about it is that I can take everything as delegate: Like images and it is just perfect for work and short previews.
To keep short: You split a problem into smaller ones (compositions!) and make delegates out of them to work faster. It is like the Bait&Switch method in Premiere, but it is much more controlled and it is a feature of AE.