To tell the truth, I don't have either, but I have a V505. I like the Moto's icon-based interface a lot more than the Nokia, but that's just me. A neat thing about the v551 is that you can modify the firmware and flex so that it runs faster and leaner. The Moto, AFAIK, has a pretty big community...
Does your friend's computer have ClearText enabled? Try toggling it on/off.
Control Panel --> Display Properties --> Appearence -->Effects
That's how you would reach it in XP anyway.
I also used to use a DI-614+. It usually had around 2 or 3 computers attatched to it. 2 via wireless, 1 with a cat5 cable. It was good for about 6 months before it started crashing.
At first, it would just start to slow to a crawl. I took a speed test on it and it was returning around 15 kbps...