crano I have only ever owned gen 1 units and they are slower than the gen 2 &3 for sure just by looking on other guys boats who have them.  Particularly when my unit hds10 has a limit of 5000 waypoints tracks etc so I have noticed the more info/waypoints and tracks on it the slower it goes.  But my units have always worked well albeit a little slow compared to what's on the market now especially with the GPS setting up for drifts.  Once your used to it though you understand the lag on the GPS and it's not that bad.  IMO I wouldn't upgrade for the sake of it operating a bit faster as for my size unit would be 2-3k and it's not going to catch me anymore fish than my current unit

Depending on your requirements 5000 waypoints isn't a lot if you fish up and down the coast and like marking anything you come across which makes me think when the time comes to upgrade I might look at a garmon

Crano.
I have a Gen 1 sitting next to a Gen 3 on my boat.
You are more than welcome to drop around and have a play with both.
I see an improvement, but its not staggering. Going from button to touch screen is a good thing though.