i am using lumia 720 since january2014 and till now i dint faced any problems,lags, and above mentioned problems at all even after upgradtion to 8.1 no problems at all,battery life is awesome,also using a 64gb class 10 strontium micro sd card and no issues at all.with windows 8.1 you have the ability store and move apps to SD cards which is cool for me coz i downloaded heavy games like asphalt8,GTA-san andreas,modern combat 4,spiderman,raymen fiesta,subway surfers,temple run 2,temple run brave,dungeon hunter,angry birds,real stell, starfleet war,monsters university( cracked) and some 512 mb ram games,and all are working fine no problems at all, just game starting time is 2-3 seconds late than 1GB ram phones,but thats ok. also you get nokia's trademark clear black display,sunlight redbility,gorilla glass 2,front and rear cameras r awesomeand belive me when you'll go to the store see both 720 and 625 side by side you will immeidetly notice the difference, i mean the display quality, and what 625 has to offer a 4.7inch screen,4g( i dont think u gona use 4g soon),and a 5 mp camera? come on man! if u gona buy 720 then i might wanna sugggest u add some 1,1500 rs more for lumia 820,u will have 1gb ram with 8mp camera with super amoled display,and u can run every game possible in windows phone.