Why does Windows 7 hate 802.11 b/g/n wireless adapters

I have been having connection issues with my Windows 7 Pro x64 system and Rosewill PCIe 250 wireless b/g/n adapter (dual antenna) over the past few months. This has been an extremely common issue with many users on numerous forums and I am not necessarily looking for advise on how to fix the issue as much as I would like to get input into why it is happening and what steps Microsoft is taking to fix it.

BACKGROUND:
Around mid-July 2012 the download speed on my Windows7 machine dropped from a consistent 1.2MBps to 100kBps (Linksys 802.11g router). I have a second tower running Vista right next to my Win7 machine, and its connection speed has stayed the same, if not actually *increased*, so I am fairly certain this is a Windows7 issue. Furthermore, only the download speed seemed to be effected; upload speed stayed around 0.5MBps. After making every tweak to the network adapter and router that I could (update drivers & firmware, change security setting, change wireless channel, and tweak most of the advanced options in the adapter configuration) I decided to start modifying my Widows configuration.

I started by uninstalling updates and reinstalling one at a time. This process was way to time consuming with a crappy connection and uninstalling updates would normally have no effect, or a negative one. I finally realized that the IE9 update had not completed correctly and by deleting the update files and starting over, I got IE9 put on my computer. This seemed to be the fix that bumped my speeds from 50-100kBps up to 700kBps or so. However, this is still not anywhere near the 1.5-1.9 MBps speeds that I am getting on my Vista machine.

ISSUE:
From all the reading that I have done, it seems that most users who are experiencing similar problems are using Win7 x64 and a wireless 802.11 b/g/n adapter. I have seen many posts of people using Rosewill adapters, but this isn't always the case.

I would like to know if other people experiencing this problem have noticed similar trends and whether or not you think it will be possible to identify the root cause of this problem (I am to the point where I think an MS update will be the only thing to fix it). If you want to post possible troubleshooting, feel free, but realize that I have gone through a few weeks of scouring the internet, so anything run-of-the mill wont be very useful.

I apologize if this post isn't a very good one, but its my first.
Thanks for your input.

-thIs

With wireless connections you need to ensure that you are using a clear wireless channel for your connection. In some cases channel overlap will cause a complete drop out of the connection, in other cases the connection will only slow down, depends on the amount of overlap in the area.

To find clear channels in your area use Xirrus WiFi Inspector.
Wi-Fi Inspector | Xirrus

As for the actual speed of the wireless connection. You can greatly speed up a wireless N connection by going into your routers settings and choosing to use 802.11n Only setting. The N only setting can only be used if you have no other clients connecting with wireless G or below, they would all need to be wireless N clients only. You can literally speed up your connection by a factor of 5 with that one setting. You will also need to use WPA2 security with AES encryption to obtain full wireless N speeds. :)