It's not that big of a deal, each company releasing new phone OS's to the wild all have their own approach. I do agree it would be nice to have full compatibility out the gate but on the other hand having a glitchy crap OS that barely runs but can play flash is not quite what people want to deal with and would rather wait for the support to come so they don't have glitchy crap

Mango will have Silverlight, Adobe flash support natively and HTML5 support with IE9 and hardware acceleration. Tethering is important but on the other hand with carriers trying to black ball tethering apps and seems GFail has no problem bending over for them... This can be tossed out the window.
There is a easy means of side loading apps as the Chevron team is working for MS on just the application as they unlocked WP7 and have ways of side loading and it seems MS is happy with them. Not like I can say the same about other companies like Apple which would have just sued them.
Storage support I can see your gripe but I'm not sure just how much storage you need. Personally I have a 16GB card in my worthless BB Storm2 and have not even used a gig of space with all the pictures and video... No big deal yet but I'm sure they will have more support moving forward but the 25GB of free cloud storage isn't a bad offering either.
I don't think the theme is terribly relevant but customization is nice. I do believe there should be a certain amount of customization that the user can apply but not something so much where they break the software and have to take it back to the carrier for a re-flash. Most users aren't that bright.
Multitasking is coming with Mango as well which seems to have a nice task manager making it easy to switch apps and see all that is running. From what I've seen with Google Hemroid is you need "App Killer" in order to manage tasks as well try to save battery. A lot of good is coming with Mango which you do not appear to be aware of.
All phones have their own strong points. iOS I feel is plain, bland and boring and the one button to do all is pretty annoying. Google's offerings are decent and I like the idea of open source but Google I don't feel quite fits the bill with their spyware tactics, ad ridden OS that is a glitchy crap with constant updates and resource hog. Need a dual or quad core just to run it smoothly... WP7 runs on basic and simple hardware and things will only get better moving forward. A nice simple and light weight OS and everything is fluid and fast. They've had issues with updates and I feel they could do a better job with venders but I feel their offerings are solid and appealing. I love Windows and I love Linux... Not a huge fan of Crapple but we all have our reasons which truly only apply to ourselves. Do what you want and enjoy what you enjoy.
I'm still waiting for Verizon to get WP7 but they seem too inept to get it to the market. I'm ready to go to AT&T or Sprint if they keep up with this BS. Should have had the phone out latest with the Sprint launch like 2 months ago but no, Verizon dragging their feet with no official announcements... Oh well time will tell.