I've just briefly tried BitMap on my iPhone 4. Very snappy! The zooming is so much more reliable on this device than on the older and much slower iPhone 3G I was using. The maps look great on the retina display.
I'll be trying out the GPS when I go for a bike ride this afternoon. It will be interesting to see how will the battery performs. I won't get a chance to thoroughly test Bit Map until next weekend.
(I was 8th in line at the Telstra store opposite the Apple store in Sydney CBD. I joined the queue @ 4:30pm and was fed from around 8pm by the stars of MasterChef. I didn't go hungry although I did have a bag of scroggin with me to get me through the first few hours. I was out of the store with the phone by about 12:30am

)