The Nextel blackberry has an excellent Speakerphone (already mentioned) - it is so good that I can leave my phone on my desk or dashboard and still hear and be heard where no other phone has been able to give me that.
The PTT feature is nice if you know others with nextel
The Antenna - ugly as it may be provides a 3dbm gain (so I read) and is such a help I can go from 1 bar to 5 bars by raising the antenna.
However the nextel blackberry is on the nextel network, so if you know someone in your area with nextel you may wich to talk to them about their coverage and satisfaction. On the plus side I have had excellent luck with their technical support and customer service.