If you've had and enjoyed an Incredible for a while then I'd say you will have just as good a time on your DX. I wouldn't say it's going to blow you away though, it's not like coming off a Blackberry Curve like I did... that's like a HUGE step up. The DX and the Dinc are very comparable, but the DX has a larger screen like you said, and the HDMI out (get RealHDMI from the market, it's well worth the price of admission). Other than that I don't think you'll find it a much different experience. But if you really liked your Dinc, then that's probably a good thing, right?
I just hope you didn't do a lot of ROMing on your Incredible. Because if you did, you may find the locked bootloader of the DX rather annoying. Like Skeet said there are some good ROMs for the X (Apex, Liberty, Darkslide, Tranquility, etc...), but no fully custom ROMs such as Cyanogen like you can get for the Dinc. But if you stay pretty close to stock, then I'm sure you won't notice the locked bootloader much at all.
Enjoy!