What do I need to know when purchasing a GPS?

[Tim.M]

My current garmin gps is now ancient (monochrome small screen, takes forever to acquire a lock, etc.)

What do I need to know when starting to look for a new GPS?

Any good recent GPS reviews or comparisons you can recommend?

I'm not sure yet whether I'll go for a standalone gps linked with a notebook as a chartplotter via serial or usb or whether I'll go for a full integrated chartplotter gps unit. In either case I need to know what I should look for in terms of the gps itself - can anyone bring me up to speed on selling points of a new gps in terms of accuracy, speed to acquire a lock, ability to hold a consistent lock, power consumption, other plus features I should look for in a GPS?