I have a 60GB PS3 and my roommate has the MGS4 80GB PS3. Neither of us have had any problems with the systems at all, however this weekend I did buy a slim because I was just too worried that my 60GB would die, so I decided to sell it on ebay since the BC models still go for a pretty hefty sum.
I have noticed the slim navigates the menus a little bit faster as my 60GB had gotten a little slow, although its not a huge difference.
The slim is also a little quieter and gets a little less hot than the 60GB did as that one had become pretty loud and extremely hot if left on for a couple hours. As far as the other features I noticed I never used any of the extra USB ports and things of that nature, and used the B/C pretty rarely. I just figured I can pull out the PS2 whenever I want to play one of those games.
Hope that helps!
Oh also if you still have everything it comes with, the MGS4 PS3's go for a ton on ebay if everything is there. You should be able to sell it and completely foot the cost of a slim if you decide to go that route.
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