When I first got my Mio H610, I was intrigued. Here was one of those "kitchen sink" devices that seemed to do a solid job in serving many needs.

Good review. I agree with you about the small screen size and complex icon-filled user interface. Just a couple of comments:
 
1. It's important to mention in GPS nav system reviews what map database the device is using. It's the single most important factor in navigation accuracy. There are only two major suppliers of maps (Navteq and TeleAtlas), and they each are producing major updates as fast as they can. The current Mio units use TeleAtlas maps, like TomTom, while most others use the Navteq maps. Navteq maps are generally reported to be a little better by users. But a lot depends on the map vintage - Mio is using a Feb 2005 edition of the TeleAtlas maps in North America, and users report they that they are fairly inaccurate in many areas of North America outside of a few core areas. Current generation TeleAtlas maps are much better, but Mio has not yet announced an update policy or price. That's pretty important to know.
 
2. The small screen of the Mio 210 and 610 handheld models is the major limiting factor of the user interface. Mio uses on OEM version of iGO nav software branded as MioMap. They did attempt to re-arrange the user interface to fit the smaller screen, but it's not entirely successful since it just wasn't meant for a screen that small. But Mio themselves make units with an identical form factor that are a bit larger, i.e. the 310 and 710 models with the 3.5 inch screen. That works a lot better. Since the iGO/MioMap user interface is highly configurable, there are many alternative "skins" developed by users which allow you to experiment with the layout and color scheme you prefer (see for example gpspassion.com/forumsen/forum.asp?FORUM_ID=37)