Make sure to completely uninstall the version you have installed before installing the new one. You will see it is actually uninstalling the previous version that takes so much time. Installation is always quick for just about every extension. The extension manager is horribly slow when uninstalling.
Personally, I often will rename my configuration folder to reinstall every extension I have rather than use extension manager to uninstall one. For me it is quicker since I store all my extension files in one place and can quickly install them.
Uninstall can take 15 minutes for me too with extensions that include a lot of files. I have noticed clearing my trash will make it much faster, and the experience on mac is pretty fast in general.
But on my windows xp machine I can install probably 30 extensions in the time it takes to uninstall one if I just rename the configuration folder. Of course I lose any custom themes and layouts I had stored, so there is the pain of having to re-serialize and re-import any defined layouts which may make using the extension manager more worthwhile for some.
I don't think there is anything WebAssist can do about it though. It appears to be a general problem with extension manager uninstalling extensions with large numbers of files. We could only solve the problem by breaking up our extensions into more extensions or by simplifying the extensions themselves, and neither of these seem very logical in response to this issue.
I guess we could create our own installer and uninstaller to address the problem as well... with the winfilecache issue of late that sounds more and more promising, but for now we are sticking with the extension manager and hoping adobe will address the efficiency problems in a future update.