If you want a lot of customization, the Android is probably your best bet. WP7 is about midway between the iPhone and Android on that front. Windows phone does "live tiles", which flip over and give you updates about an app without actually opening it.
I had a Windows mobile phone about 4 years back too - HORRIBLE. Windows Phone 7 is a completely new platform and absolutely nothing like its predecessor. App count is 28,000 and growing faster than the other platforms when they were at the same point in the market.