I only had mine for a few months before it was stolen, but I'll get another. I'll willingly purchase a Garmin. I had the Nuvi 200.
I got a Nuvi 205 for Christmas. It seems okay. What I really think would be cool would be to have a way to download locations from your computer via USB straight from google maps or whatever
You can already do this. Read your manual. Look for POI (Points Of Interest), and then add whatever you'd like. If you need more involved POI's than that, google POI and Garmin. They make POI loaders, and you in fact CAN download something from Google Maps to your GPS. I can't remember if it's Google or Mapquest, but there's even an option to download your directions or POI or whatever it was right to your GPS. It may be that your model can't do that, but my model was the step below yours and it could when I had it, so I'm guessing yours can too.
Both suck. Get a TomTom.

Take note of everyone who is in favor of TomTom's. Everyone who has chimed in with "any other maker sucks" isn't from the U.S.
The reason I went with the Garmin is because I live in Wisconsin. There is one other city, and I believe it's in Minnesota, in the U.S. that uses the screwy addresses that we have here, and nobody can seem to handle these except for Garmin, even those that use the very same NavTech maps that Garmin uses. For example, an address I might be trying to find: N55W16436 Richards Drive. The best (apparently) that any other manufacturer can do is give an approximation of the nearest cross street, if it gives anything at all.
TomTom's are useless to me in my state if I have to deal with those types of addresses at all, and unfortunately, I have to deal with them on a sometimes-daily basis. I specifically tested this with several addresses in a store, just to see if they'd come up with the address, and the Garmin gave me directions about twice as often as any other manufacturer, and gave me options that were close/same block as what I was looking for far more often than any other manufacturer as well.
Given that a Garmin is all I have used, and all that I will use in the future unless this specific problem is addressed and solved by others, all I can obviously recommend would be a Garmin, but even if others can deal with the issue, I'd still be skewed towards Garmin. Nice little units, reasonable cost (I actually got mine at a Target B&M store because it was on sale for $15 less than the best price at Amazon at the time), and easy to find accessories for in my area.
The little card slot is to carry more maps, POI's, pictures (why, I have no idea, but whatever), music (some play mp3's, although the sound is obviously not going to blow your socks off), etc.
When I got my Garmin, I instantly updated the maps to the latest version possible, and I found that while on a construction site, it had the road I was on and the actual name of the road, even though there was no street sign. I asked one of the guys if that was going to be the name of the road, and he seemed a bit surprised that I knew this, given that it was being paved that day, and again, was ON a construction site that no one other than them and myself were allowed access to, and no signs.

I dunno what maps Magellan uses, but IIRC, the better maps for the U.S. are from NavTech (I think that's the name, not positive on that though), while the other main map "people" are better for Canada and Europe. The TomTom uses the other map "people", which in my mind gives one reason why they would be more popular to those people outside the U.S.
My wife was able to figure out how to use my Garmin without a manual, so I highly doubt there's some brain teaser that's inherent to ANY GPS, really.
If I did a bit of hacking, I could have added other voice packs to my Garmin (need that memory card, though), and without hacking, was able to add several custom markers for the maps and vehicle icons as well.
As for which to choose, look around and read some reviews. I had a few places bookmarked, and can't find 'em anymore, but I did come across this interesting nugget from a review site about Magellan. MIO seemed to make decent cheap units lacking a bit of the functionality of more expensive units, but I dunno what their rep is recently
http://www.gpsreview.net/magellan-sold-to-mitac-mio/I sifted through their forums for a bit, as well as this site too:
http://www.gpspassion.com/fr/Default.asp I liked this site better, simply because they had a few more things already sussed out for me at the time, such as POI's and a list of reviews of Garmin units I was looking at at the time. IIRC, they've got some info on loading different voices there, but there were many sites I was looking at in researching, so....