I was considering replacing my old PS2 with a newer PStwo, as my current system has been having trouble starting up dvd movies lately, but I've heard some bad things thus far. Supposedly, heating up is still a significant problem with the system (some claim even moreso now than with the old version) - many reports of the system overheating during long sessions of GTA:San Andreas. Secondly, it's still pretty loud, so it's not ideal for watching DVDs...
And as far as the toploading/swap trick, I've heard that it won't work without some modification (it has a slightly more complex way of telling that the lid is open than on the ps1).