The N900 is my first device with gps built in, but I have to say that I'm very very satisfied with it (using Sygic). The lock time usually is under a minute for me outside my house (in the house it locks within 10 seconds of starting Sygic). My brother has a Samsung Galaxy S2 but sometimes the built in gps on that is crap, so he uses the Sygic gps for android which is pretty good, although his signal tends to go every now and then. For me it only happened maybe twice that the signal was lost and couldn't lock again so then i restarted Sygic and all good. I have been using Sygic for more then 6 months now and it's a great gps program.
I also have a program called GPS recorder, it can show how many satellites there are and what the strength of their signal is. There are other features but this is the one I find interesting.