G'day, just chiming in here to offer my thanks to the OP for this ROM. I have a Y300-0151 model in Australia which were only $85 on sale from Dick Smiths. The hardware is absolutely great for the money but it's really nothing special compared to the galaxy or nexus ranges. The stock 4.1.1 ROM was actually quite slow just navigating around and often laggy swiping between things. I rooted the phone when I first got it several months ago to overcome the issue 4.1.1 had with saving paid apps to a location which does not load on boot (meaning you loose them and all accounts and settings related to them every time the phone is rebooted). I overcame this issue by backing up my paid apps with titanium backup and restoring from the backup but that meant that I could never allow the apps to update from the Play Store. As soon as they did, they were back in the non-boot location and lost upon restart.
I put off upgrading the ROM for a while because there just didn't seem to be too much available for this cheap phone. Did some research yesterday and decided to go ahead and install the Slimkat 4.6.2 build (latest available) linked in the original post. There wasn't any information available on whether or not it would work with my 0151 variant of the Y300 but hey, it is only an $85 phone so worth taking the risk. I'd like to say that it all went smoothly but I did have a couple hiccups. Nothing to do with the ROM/hardware compatibility though.
First problem was actually upgrading TWRP recovery. Goomanager app wouldn't work. I ended up having to flash the new version the old fashioned way. I didn't try to flash the new ROM until after I updated TWRP recovery so can't say if it works or not. The instructions on the Slimkat site are pretty clear though that TWRP must be upgraded first.
Alright, backed everything up to my ext SD card and flashed the new ROM. Then without leaving recovery, I flashed the gapps package (used the full Slimkat package). Rebooted and viola! it works.
Second issue, I lost root access? What, surely that can't be right. Googling a bit revealed that the Slimkat ROM has root access disabled by default. That is a very strange choice for a custom ROM that requires root access to even install. Anyway, that's how it is so I'll just turn it on again through......... what?? Developer Options is also missing. Another very strange choice for a custom ROM. OK google came to the rescue and after 7 taps on the "Build Number" in the about phone settings menu my Dev Options were functional. 2 seconds later and I had root access enabled.
After restoring apps and data and setting everything up and testing, I am pleased to say that I do not have any problems whatsoever. Everything is working fine. The best part however is the difference that kitkat has made to just navigating around. I read that most of the changes to Android in 4.4.2 were streamlining coding to enable flawless running on lower spec hardware. I can honestly say that this is VERY noticeable on the Y300. There is no more lag and jitter and waiting for it to catch up to my gestures. I would go as far as to say that this is a "must do" upgrade on the Y300. It has made my $85 phone perform as well as my previous $700 phone (well, almost anyway).