Great thread here... I also was trying to decide between the SF and the Dinc. Ultimately it came down to battery life and screen quality. I'm coming from an iPhone 4 so both are a concern to me. After reading tons of reviews and watching youtube videos I went with the SF because I felt it was a better device.
Having said that, I just ordered mine today and should be here on Thursday so I'm quite happy about that. I'm eagerly awaiting the 2.2 update but until then I plan to root and explore what android has to offer.
I think you will enjoy it. It's easy to root and mod, and lots of roms are going to be coming down the pipe. The Galaxy S variants worldwide have a huge and very supportive following.
I completely bricked my sister's fascinate while rooting and de-bloating. Took me an entire day to fix it, but fix it I did. I'm nothing if not persistent ...
Anyways. I finally got it working again, rooted it, de-bing'd it, de-bloated it, and launcher pro'd it (which doesn't take long at all provided you don't brick your phone!!!) The screen of this phone, the ergonomics, and the battery life are the main things that make this phone a champ of a smartphone. I am loving mine, and my sister is loving hers, and we both love our Fascinate's more after rooting.
Is it a requirement? No. Is the phone great without it? No, it sucks. HAHAHA! I kid, I kid!! Even not rooted, this is still a beauty of the phone, and installing launcher pro, which is well worth it, doesn't require root.
There is a wealth of information on these forums that will literally help you make the Fascinate (or most modern Android phones for that matter) into your perfect phone.
I read some advice on this forum, and I can't remember who wrote it, but it is so true, and so golden for making your decision.
Make your choice based largely on the HARDWARE that best fits your needs. Why base it on the hardware? Because the software issues of these phones will be taken care of by future updates. And if Samsung doesn't fix these issues, THE ANDROID COMMUNITY WILL.
I have owned a Droid X, which is another excellent device that also benefits from rooting, but has advantages and disadvantages over the Fascinate. I'd look into that one too, especially if you're in a shaky reception area, or use your phone in a lot of noisy environments.
Or hate glossy plastic on the back of your phone....