I have a Focus and an HD7, both up to Mango, and I don't see any particular brightness changes going from app to app, ie or otherwise. Could be a store demo issue. I guess you would say I went from iPhone to WP7. I mantained Windows Mobile devices while the iPhone was my primary for a year or two. Right now the Wp7 is primary, though I still have an iPhone 4 (no SIM but makes a decent GPS, Media player and apps platform). I find WP7 easier to get around in and get normal things done, as is evidenced in Ben's $100 challange videos from CES. It is a very nice and smooth interface. You are never going to get away with having everything integrated into an OS, so there will always be some, run an app, get out, run another going on. WP7 does a good job with this and even makes some app access slicker by offerring links in other apps for typical next steps. Photo manipulation available from the picture hub for example.
There are certain things that are still lacking, but that is only significant if they are important to you. Tethering and Visual VoiceMail are dependent on phone and carrier. We don't have a Starbucks Card app yet (!#$%#@!). No Skype client (WTF? MS owns them?) Beyond Nokia mapping/navigation/GPS is a bit limited, thought there are some good products out there if you are OK with actually paying for other's efforts. Bing Maps is OK, but I tend to gravitate towards off-line capable apps.
I don't miss my iPhone, 4 BTW, no Siri. For a lot of things the voice capabilities of WP are sufficient. I feel silly talking to my phone anyway, so rarely use that capability. Games seem good to me, but I'm not the guy to ask about that. I'm near 60 and I enjoy Kinectimals.
The thing that disappoints me most I think is the Office Hub. I think it is layed out poorly and it is difficult to work with off-line files. Even with the new SkyDrive app, I have yet to find a way to organize files in off-line folders, and you of course can't make any on-line ones. MSs cloud Office offering, Office365, won't let me save files to my sharepoint portal (only save to Skydrive). Dropbox and some of those do have some support. The business side is just severely lacking IMHO, at this point. That wasn't there target at this point though, and it isn't all that much worse than any other platform.
I do find the Outlook/PIM stuff excellent. I do way more e-mail triage on my Focus than any other mobile device I've ever had. It is actually pleasant. I'm not going to write a book response, but I find it very easy to keep up with my inboxes, and calendars. I do wish I had control over what was quoted in forwards and replies though. Sometimes I need to reference what I am replying to, but not perpetuate the other 15 e-mails in the chain.
So, I think you will like the OS. Coming from iPhone, the question would be, is there any obscure app you can't live without? (Starbucks Card !#$%#@!). Most of the basic functionality, other than that is covered, and it is covered much more elegantly.
BTW, I have an android tablet, no phone. I enjoy the widgets and such, but it doesn't appear to do more than WP7 or iPhone, just does it differently. It reminds my a lot of Windows Mobile. I'm just past wanting to futz with my phone a lot. I do need to make some personal changes, but I don't need 'customizing my phone' to be my hobby. WP seems to strike a nice balance between iPhone and Android in that respect.
Sorry, you caught me in a gabby mood