I have had problems with mobile network and ram consumption on Fremantle. Maybe this is old news for others but after I had been watching one yellow blink on top bar telling me that there are updates which I do not want to install I thought that I will put off all repositories so that the updates are not fetched anymore. Everyone else has probably done it from the beginning of time. I did it now. Wow. Ram consumption dropped down and connection seems to work much faster. I learn very slowly. I had 5 repositories on all the time and 75% ram used.It dropped to 45, and now browser open plus conky it is 65. I have desktop widgets (yellow notes plus dockbar) which probably eat some as well as simple green theme and a wallpaper.

Would like to know what is the level of ram usage if you have only conky open? I mean maybe I have something else wrong too.

After regular updates stopped being a thing on the N900 someone posted an edit to the appman config file to have it no longer scan the repositories daily/weekly/every connect etc.
Appman really drags down the phone for around at least five minutes looking for updates that are not really coming anymore every time you connect to any kind of internet.

If your not using the community (CSSU) version this was much improved regarding performance and bugfixes. apt-worker being 40% faster than original code.

The way I understand it there will always be a limitation on how fast HAM can be due to maemo packages having there icon data encoded in the control files.
Minimise the amount of repos you have enabled will speed it up, if you don't wish to edit the update timer value hidden in the backend.