If you want your blog to stay as fast as possible and you want to support mobile users you will have to reach some compromise.
This was true until today. With the WordPress Mobile Pack version 1.2.1 you now can get the best of both worlds. Here is a quick guide on how to achieve it. I am assuming you have installed the latest version of WP Super Cache, already.
1. Activate WP Super Cache
2. Go to the WP Super Cache options
In your admin -> Settings -> WP Super Cache
3. Turn WP Super Cache ON and mobile support
4. Click on Update Status
5. Scroll down and click on Update Mod_Rewrite Rules
6. Make sure WPMP is active
Go to Plugins -> Installed and activate WPMP if not yet active
7. Enjoy speed and mobile content at the same time!
Notes for the geeks
Setting up WordPress this way will generate some extra cache files because you will have a cached version for your desktop versions and up to 3 versions of your mobile site depending on the devices that visit your site. Don’t worry about this too much as Super Cache will clean up old files anyway and if most of your visitors are in the same device class you will not get the other cache files generated.
The integration works in a way that WPMP gives to Super Cache a new key to cache files, so that desktop and mobile pages are separate. Super Cache will be only partial (i.e. like the HALF ON setting) for your mobile content, but and send static HTML files for desktop (i.e. the ON setting). This is currently the best we can get, but soon it might be different, so stay tuned.