I live in Montreal, and do plenty of city driving.. it performs well in canyons, I have no problem maintaining lock.. and have never seen it drop below 4 satelites, in the deepest parts of the city. When I pass under overpasses, if I'm going a good speed. the iguidance car icon doesn't even blink to red for that split second on me...
Sxott, actually.. I learned that if you power the gps down, and then power it up again at a different location, it takes much longer to attain lock.. this is because it stores its last location data in the memory, and attempts to do a quick lock with this data.. if after a minute it can't do a quick connect, it goes through a standard coldlock, which can take another minute.. so if you relocate it, it can take up to 2 minutes to relock... I've never had any problem with mine, though.. and I always park inside a parking garage.. it gets lock before I'm 100 feet out of the garage door.
I dunno what the differences are with sirf 2 and 3.. ayay claims to have a better sensitivity compared with some SIRF III units, so I dunno.. sirf3 is a different chipset compared with sirf2.. which definitly makes a difference, but antenna design and other stuff i dont know a thing about are to be taken into consideration as well. Maybe someone with a sirf3 could test the ayay to give us an idea of how it compares?
One reason I think it does so well is that the antenna has a solid titanium baseplate (the entire casing) to make a groundplate.. but I could be wrong.
At any rate, I'm very happy with my AyAy.