I just bought the wife the motorola T505
I gotta say I love this thing with the Iphone 4.
FM Transmitter works awesome, calls sound good, (mother in law told me I sounded very good on her end)
Bluetooth to FM Transmitter for Music was amazing, i have a cheap FM modulator I use now, but i get whine and static. Using the T505 was crystal clear. I cant say enough good things about it. But Again I only had it 2 days now...
Winky
I have this one as well, based on the recs from people here. Mostly, it's been a good piece of kit, but a few small issues:
-I've had occasional complaints about an echo from my end when on a call.
-The FM transmitter works best if your antenna is near the front of the car. If it's in the back, the transmitter is less effective.
-If you're in a metro area, it can be difficult to find an FM station that works. This is compounded by the fact that there's no way to set ONLY certain stations for use or to set a specific station by number. It's also not easy to quickly change the station on the unit without looking at the unit as the button is very small, located in the rear of the unit, and about half the time when pressed it turns the transmitter OFF rather than changing the station.
Overall, I do like it a lot. It's great to be able to have my Navigon directions broadcast through the stereo, along with my iPod, and I much prefer calls through this than using a Bluetooth headset. But it definitely could be significantly improved.