No you cannot be on a voice call and surf the web or send emails. Voice calls, emails, and the web browser use grps and sending an sms uses gsm. Therefore, you can send an sms while in a voice call or receive a sms while on a voice call.
Not until the next gen- UMTS. Then we will be able to do voice and data at the same time. EVDO next revision same thing. This will be a major breakthrough.