Yes. You should definitely either switch or keep the Fascinate. Personally, I'd go with whichever phone I liked better
It really is a personal choice. What don't you like about the Fascinate? What do you like about the D2? For me the only thing I like about the D2G is that it's got a GSM radio, if the DX had one I'd probably go there for both phones (or, more likely, someplace else for my play phone) because of the larger screen and lack of keyboard. Many (most?) people here love the D2 keyboard, I'm sure it's also why Pro owners went with their phones but the keyboards are very different. Or are you looking for CPU horsepower? If so, what applications do you use to stress the CPU (graphics vs. calculations)?
Will the D2 make you happy? Should you wait for the next generation phones? Are you moving to Motorola or away from Samsung? Do you like the interface on the Motorola better than the one on HTC or LG? All of these are questions only you can answer. Here you'll hear that the D2 and D2G are great phones with excellent build quality. Of course you'll probably hear a lot of similar things on the Samsung forums.
I would go with the Droid 2 Global. It is a better phone all the way around. I just dumped my Droid X for the D2G and even though the X is a killer device. I like the Droid 2 Global better. The Fascinate doesn't have anything on either.
Depends on how your going to do the switch. If your rich and you don't need to use an update and then go ahead and switch, D2G is a great device. But if your not rich then i would stick with the fascinate and wait for dual core or more of an upgrade (i guess 2.2 is a huge upgrade but you know what i mean, spec wise) One thing that should be noted is that you will feel like the screen is a lot smaller. The moto's have really really wide screens and it makes them feel smaller. My ipod touch screen (3.5in) feels bigger than my D2Gs(3.7) simply because it is much wider.