If you belong to a 'Wholesale Club', I suggest you check there first. I also suggest that you borrow one before you buy one. I was ready to buy a GPS, but borrowed a friends before I bought one. His was a Magellan and in one trip I was able to figure out 2 or 3 things that I HATED about his. When I did buy one, I went to BJ's and they carried TomTom, Magellan, and Garmin units. About 8 months ago I ended up getting a Magellan (a different model then my friends) for $99 ($119 - $20 Instant Rebate) + $10 for a 2 year warranty. Add NY tax and I was out the door for about $120.
Wholesale clubs usually have pretty good return policies. The guy @ BJ's said that I had 30 days to return it, even for something as simple as I don't like it. I didn't end up getting a 4.3" screen, since the ones I looked at seemed to be shorter then the 3.5" screen. Frankly, in a GPS, I wanted height, not width. What good does seeing more stuff on either side of you do? You really want to see more stuff in front of you (not to say that all displays just show more map info on either side of you, some seem to have slightly larger icons, etc.). The ones I looked at showed no benefit for me to have a wider screen. I definitely wanted one that had spoken street names (I work in NY City limits, I really don't want to be looking at my GPS while driving). I'd bet that in more rural areas, that wouldn't be such a big deal. I'd say a lot depends on where you live and your personal tastes. I'm sure you know someone who could spare theirs for a week or weekend and not miss it. I think I have needed to use my GPS about 6-8 times since I've owned it.
-Ken
BTW: You profile shows you live in Boston. I don't suggest you attach the GPS to your windshield if you park your car on the street. The suction cup leaves rings on the Windshield which let thieves know which cars likely have a GPS in their glove box. See about suction cupping it onto your instrument cluster (over a clock, that icon showing which doors are open on your car, etc..). For me, mounting on the instrument cluster keeps it a bit more shaded (making for easier viewing), lessens the chance of it being stolen (no rings on the windshield) and lets me hear it better without having the volume cranked.