The main problem with the 7750 is that it is a half-step in the BlackBerry development. It has the processor of the older, black-and-white, 6750 but shipped with a much more graphically intense operating system. The 7750 is constantly fighting against processor and memory limits even during basic operations.
When I was running a 7750 I found that if I were actively working in any application (composing an email, for example) calls would either go straight to voicemail or, even worse, ring through and cause an hourglass to appear and sit there taunting me and preventing me from answering the call.
The 7130e is a dramatic step forward in all areas: processor, memory, screen resolution ... add in speakerphone, Bluetooth, EvDO, and tethering support ... You'll be very pleased with the difference.