This bugged me enough to take another look at it...
If you follow the instructions below then Gmail will pick up your Google contacts so you it will auto complete as you type the name in the To: address.
"I don't use google mail" - Well nothing to stop you creating a dummy account and importing all your contacts in there. You could collate your mail accounts into that via pop3 or just use the default email client which will STILL use your google contacts anyway!
If you install the calender and contacts sync adapters as found here:
viewtopic.php?f=48&t=1775. In CalenderFix.zip are two apks. install BOTH of them.
You can also install the "Accounts and Sync" from the above or use "AnyCut" application from the market to add a shortcut to "Accounts and Sync" which is already on the phone but hidden. Configure this to sync contacts etc with your chosen google account. Or even ADD one if you haven't already, I made a special new gmail account just for the scroll since it is shared with my whole family, I then linked it to my Samsung phone first before linking it to the scroll...Worked fine.
Thats it, once the sync is complete start typing the name in GMail/Email and it will auto suggest your contacts.
Better still! You can also install Go Contacts EX via apk (Market will hide it from the scroll, just google "Go Contacts EX 2.05 apk"), which allow you to manage all your contacts and even email direct from the app! Of course you can still manage all your contacts from the web browser in google.
For my 2p worth, I actually have a web shortcut on my home screen which goes to my hotmail and I use the web client, yeah its not exactly a "push" client but I don't like any of the mail clients anyway
Still not ideal but better than a slap in the chops I say, hope that helps someone.