The battery lasts long before 830 uses ips screen. 930 uses amoled that consumes more power when you browse web page and anything that uses white color.
Try use class 10 memory card.
Been using this phone for a while, like few days... I'm going to say this phone is not that bad when compared to L930. Here's my first impression.
What I really like about this phone is, it is much easier to hold it in my hand compared to L930. I have some trouble trying to reach the opposite side of screen (reaching right with thumb when holding with left hand) with my L930, I don't have much problem with L830. Understandably, the screen size is the same with L930 so I'm betting the thickness is playing the role here.
Despite the lower resolution, I think I like the screen more except that the color is a little washed out. I guess that's the advantage of AMOLED on L930. The black on L930 is blacker as well. But the one on L830 looks smoother and feels snappier.
I also noticed that L830 has better music reproduction as well, but I might be wrong here and I probably need to verify this but if you like music, I think you will like L830. SDCard memory expansion is welcomed for most people, but I don't really care much as I tend to keep most of my stuff on cloud anyway and my full libraries of MP3s are still around 2GB. I can't even fill 32GB space of L930.
However, I do have problems with this phone. Mainly, playing music over bluetooth. Somehow I think Windows Phone isn't really capable of handling this properly when the music is on SDCard. I keep on getting skipped audio whenever I play MP3s from SDCard. I do faced this issue before when I try L525 but L525 handles MP3s over bluetooth a lot better compared to this L830. It could be due to my old Class4 SDCard, but unless SDCard and Bluetooth is tied to the same IO I don't think any phone should have problems handling MP3s over bluetooth with such card. As this is a feature that I use daily when driving to work, this is really a turn off for me. Luckily I have Spotify in such ocassion.
I also am facing frequent crashes with my frequently used apps. I don't know why. It could be some updates for these apps are needed for Denim, or it could be the fact that I'm using a device with 1GB RAM like it has 2GB. Not exactly a game breaker for me as I've faced worse on Windows Phone previously but annoying nonetheless. Your mileage might vary though.
Gaming performance, I didn't really thoroughly test at this point but I'd say playable based on the most unoptimized, incomplete game I've seen Windows Phone Store; Angry Birds Epic. Framerate isn't as high as L930, noticeable with my eyes but it didn't really bother the gameplay. So, I would say you shouldn't expect any bad gaming performance on L830.
And, I dont know what sorcery did Microsoft apply on this L830 exactly but the battery life is phenomenal. It's actually much better compared to my L930. My L930 previously will always drain the battery around 4% - 5% per hour but this L830 hits impressively lowest 2% - 3% per hour. It could be that at that time not many background process is running yet but after 12hours, the phone consumed less than 50%. Even with my lack of usage I'd say that is impressive. Maybe next few days we will see the true colors of the battery life, but it is worth noting that my heaviest use was 11% - 12% per hour drain while on my L930 I can hit 15% per hour easily. Microsoft must've applied some sort of black magic here.
As for temperature, I'm very satisfied with this phone. I don't feel the warm I usually feel when I use L930 for browsing. It's a pleasant phone to use if temperature is your concern. In fact, this phone is the most comfortable phone I've ever used in terms of temperature so far.
Unfortunately, this phone is using Snapdragon 400 so it doesn't have "Hey, Cortana!".