I've been using a Nokia N97mini for a little over a year prior to getting the Inspire. My two major reactions to the switch:
1) OMG! This screen is huge!

2) OMG! This phone is fast!
Apart from that, Android is so different from Symbian that it will take some time for me to learn it well enough to make a fair comparison. The ringer/speakerphone is definitely weaker in the Inspire (the N97mini had dual speakers that were LOUD). Not a concern for ringtones since my phone is always with me, but I'll probably have to go back to using my Jawbone for hands-free rather than the speakerphone.
I'll miss the Carl Ziess optics on the camera, but the Inspire's 8 Mpx shooter can do a decent job if you follow the advice in
[GUIDE] Desire HD Camera guide - all issues resolved - xda-developers.
All in all, the Inspire 4G is a great phone at a great price. There will no doubt be "better" phones before too long, but I suspect it will be some time before another hits the same value "sweet spot".