Apps are not deal breaker for me but the below are possibly. What you think and what else?
- FM radio no more(as I read from reviews. iHeart and TuneIn can help but not for data limited users)
- Wireless sync removed (Who in the WP team decided that it's not needed? I don't even remember connecting my phone to my laptop for a long time)
- Notification center or lack of.(Good news is that it might be possibly coming in 8.5 in another 10-12 months?)
- No free turn by turn for non-Lumia devices(?). (Not much important as others as I use mass transit heavily but could be for many)
Possibly, still my native language is not supported in spite of another 50 languages. I don't want the entire phone OS in my language but atleast the browser and apps should be displaying the font. But file this under 'not sure' as I didn't find a complete list of new languages added yet. (iOS had support from 3.0 and Android I believe from ICS) Edit:- Tamil is supported now. Check in comments for the link from Heman.Vaigundhan. Thanks.
- Lack of VPN support
- Lack of IM backgrounding support(Not sure) for IM apps especially a jabber client for me