High download speeds, slow browsing speeds

It could be that there's a DNS problem somewhere. Web browsing tends to involve a lot of small connections, with several DNS lookups just for one page, whereas large file downloads only need to make one lookup. So if there's an issue with your ISP's DNS servers, it could be slowing down your web browsing without affecting your large transfer speeds.

Try switching your DNS to use the Google Public DNS servers. Open up the Network pane in System Preferences, select your wifi and click Advanced…. Then go to the DNS tab, and enter in 8.8.8.8 and 8.8.4.4, as shown in the screencap: Make sure those entries are above anything else in there.

It may be another issue, but this is a good starting point.

Increasingly ISPs are hijacking DNS traffic. You can put any ip address you want into your preferences, and it will be captured at their gateway and redirected to their own server.

A partial answer is to run pdnsd on your local machine. Give it a large cache, and set it ignore time to live that are under 24 hours. This will reduce the number of dnslookups you have to do.

On applying this to my home network (4 computers a 2 Mbit down, 500 kbit up, satellite link=high latency) doing this made the network FAR mroe spritely.

The second solution is to buy a share of a better connected host that offers VPN services. A friend did this and found that even with the overhead of encryption it was still faster by a factor of 3.