Have you tried the internal Wifi with a newer Linux distribution? I'm using Ubuntu 15.04 and it works great :) No disconnects, speed good be better though ...
Regarding a replacement: What do you think about the Librem 13? It's one of my favorites along with the Dell XPS 13 and the Lenovo X1 Carbon.
I'm running Mint 17.2 which switched to following Ubuntu LTS releases only. So, I haven't tried a newer Ubuntu, but the wifi is terrible in Win8 too. The "Panda Ultra 150Mbps Wireless N USB Adapter" http://www.amazon.com/gp/product/B00762YNMG was my solution for a massive range/reliability increase.
I'm really happy to see the Librem 13 nearing existence, but it's not ideal for me: i5 only, no back-lit keyboard. Up to 16GB and the matte screen is awesome though. The X1 Carbon 1st/3rd Gens are great, but Lenovo is being so bad recently.
I've seen it, but it only runs 6hrs (vs 10-14hr) on the battery, weighs 2X and costs 2X my current machine. Plus 15" is too large. I'm really happy to see the progress on freedom-respecting hardware, I'm just not willing to make that many sacrifices at this time.
Have you tried the internal Wifi with a newer Linux distribution? I'm using Ubuntu 15.04 and it works great :) No disconnects, speed good be better though ...
Regarding a replacement: What do you think about the Librem 13? It's one of my favorites along with the Dell XPS 13 and the Lenovo X1 Carbon.