I agree that the voice prompts are excessive. The first prompt seems to be based on speed. On the highway, I get the first at 2 miles. but off the highway, I get the first at 3/4 or 1/2 mile. This is fine, but I really don't see a need for any more until I'm close to the turn.
What I find the MOST annoying is the "In 400 feet, enter the highway...". Well DUH, I'm already on the entrance ramp! Do I have any other choice?... 
Also, Teleatlas needs to continue to improve their map data. I had to drive up to Danbury, CT yesterday. On my way back, I got ZERO prompts where I-84W splits off to Route 7. It's not a minor interchange. The two right lanes are for I-84, while the 2 left lanes are for Rt. 7. It didn't even provide the 'recommended lane' arrows. The map showed me which way I needed to go, but there were NO prompts. At other places, it warns you like crazy to "Keep left!!" when there's a normal right-side exit. I have sent TeleAtlas a handful of corrections (mapinsight.teleatlas.com). Let's hope they listen (and Pioneer offers updated maps on a regular basis).
I thought the "Warn when speeding" function might be nice, but it warns me every time I enter the freeway. The speed limit for the entrance ramp might be low, but I'm accelerating to get to highway speed, so there's a really good chance I'm going to be going faster than the speed limit. It goes off even when I have it set to 100% (which I assume means twice the speed limit), so it's now turned completely off. Great idea, but useless in the real world... 
-Eric
By the way, has anyone else noticed that, after the update, Samantha now pronounces "take the next left/right" as a question? Her voice goes up at the end of the sentence... 