Buying New Nokia Lumia Help me !!!

Currently I am using my iphone, I am really bored using the phone, Now I am planning to go for Nokia Lumia. I got 2 option with me Nokia Lumia 800 and 900 and also I have noticed many people on this site are complaning about nokia lumia phone. I am not a music freak, but I want my phone must be very fast and UI must be very good. I have read many article on this site stating that while using headphone the sound quality of Nokia Lumia 800 is not good. For 900 there is rattling noise in the device. Did you nokia fixed this problem or not.

I require your help on the below points.

1. Battery life of Nokia Lumia?
2. Nokia Lumia 900 has touchscreen lagging issue.
3. Lagging problem can be fixed by any application ?

Most of the time in a day I use my iphone, and my 3g service is always on in my iphone, I can easily squeeze a day of heavy usage out of one battery cycle. I would get the same or better exprience while both these device or not ? I am more interested to hear your comments on Nokia Lumia 900.

Well as far as I know Nokia lumia 900 sounds great while listening to music via headphone, If I talk about iphone there is lagging issues in the software which is addressed. In my opinion, nokia lumia is good but people make it bad. I don't want to comment anything on nokia lumia 800. Don't think pretty much anything unless you're coming from another WP7 device.

Which headphones are you using? Want to know if theEtymotic ef-5's will work...with Nokia Lumia device or not ?