128kbps is pretty slow, but it's fine for basic use. That's basically a mediocre EDGE connection like the original iPhone without great coverage, and while it was no speed demon, it was certainly usable. It'll let you send instant messages, and check your e-mail and get directions if you're patient. I could easily see surviving on a plan like this while traveling.
I've been in Canada for a year using my UK phone, so I only get Edge due to the different bands. Surprisingly, I have survived and I didn't think I would. Sure things take longer to load and I can't really stream YouTube but you learn to live with it and you can always pick up wifi in a lot of cafes and restaurants to send images and files. But, I can send/receive my emails, use Tango/WhatsUp/Skype to instant message, Facebook, browse the web etc. It's more than adequate, you can work around the limitations fairly easily. I'm also on a limited data plan (500MB month) so at faster speeds I would hit that limit very quickly!
I will be buying a Nexus 5 when it comes out though :)
