I am seeing the same strangeness with the GPS on my N810. The fix times are usually (but not always) worse than my Holux GPSlim 236 (never better though).
My understanding (from this forum) is that the unit is sirfIII-based, same as the Holux. I am betting a software issue, not hardware - they are using a gpsd based off of 1.0 (-23) -- the current version is 2.34...

I'm also a bit disappointed in the provided mangement software (and its closed source nature) -- no documentation on how to use the gps wrt power on/power off. I would love to be able to have the GPS unit power on every half hour or so and stay up long enough to get a fix, then power off, even if I am not using any nav software at the time. I think gnuite solved this in MM, so I'll take a look at how he is powering the unit on/off.

Advice to those with fix problems, find it a nice spot near an equator-facing window in a single story house, start the location applet, prop it on its stand and walk away - check back after having a beer and it'll have a fix - it does seem to be faster the second time.