I went ahead and bought the phone on T-Mobile this morning (via Carphone Warehouse) and the phone itself has no branding on the case. The only visible software branding I can see is the 'Web 'n Walk' icon, which I'm not too worried about. Assuming by VOIP you refer to the 'Internet Telephone' options these all still appear to be available though I'm not able to test at present.
I then phoned Voda to talk to them about getting a PAC code for transferring my current number, and of course got the usual grilling about why I didn't want to stay with Voda. I told them I'd have been happy to stay, but:
1. When asked about an upgrade they wanted to charge me ?350!
2. The phone I was allowed to test (for only minutes) in a Voda shop had Voda branding all over it.
His response - they'll now do the upgrade for ?50 while stock lasts, and the branding (software obviously) is all changeable. I could have lived with the Voda logo on the phone if I'd known this before, so I'd say they shot themselves in the foot there by offering a crap upgrade deal to begin with. Of course I don't believe there's any way to cancel the T-Mobile contract now even if I wanted to.
Grrrr.