iOS 5 notification center has got lots of minor jailbreak tweaks which give additional functionality however BlurriedNCBackground Jailbreak tweak will change the way iOS 5 notification center looks. As the tweak replaces the background with transparent glassy background that allows you to view background homescreen while using notification center. Although the Jailbreak tweak is free but its still conflating with IntelliScreen X for which the developer is committed to resolve.
BlurriedNCBackground Jailbreak Tweak description as per developer,
BlurriedNCBackground has some configurable settings to help with the kind of device that you might be using. Certain settings will produce less lagging than others on older devices. Devices like the iPod touch 4G and iPhone 4 will not have any real lagging problems. I have both devices myself and this tweak runs as smooth as butter. If it starts lagging for you it’s because you have too many notification center widgets installed. Plain and simple. Look at my Notification Center and you will notice that I am a minimalist and do not use any additional widgets, only the stock ones and the ones that come with IntelliScreenX. Devices such as the iPod touch 3G and iPhone 3GS may be more prone to lagging due to the nature of the slower processor and less RAM. Albeit some devices are faster than others, you can try out the settings for yourself to use what best suits you.
You can install this free Jailbreak application from ModMyi Repo in Cydia.