Client-side caching is not a problem so long as you set the correct cache control headers on the content you serve.

I can't say anything about the (possible) dial-up issues since I haven't even seen a dial-up connection since about 2004.

I've made my views on this more than clear, so I'll say no more on the topic until (if?) a Linode staff member weighs in.

Most websites these days (including this forum) already use gzip to compress all plain-text content. SSL is applied after compression. I can't quite remember how modem compression used to work -- hey, it's been a while since I used dialup -- but surely it can't gain much by trying to compress what has already been compressed? (Headers might compress better.)

It's true that gzip-compressed traffic doesn't get compressed further by the modem. But (surprisingly enough) there are a lot of sites out there that don't use gzip. It's fun to see my throughput meter spike above 10 KB/s.

SSL encryption prevents modem compression regardless of whether the traffic is already compressed or not. So you're dependent on the server admin having set up gzip (and cache control) properly. I wish the "everyone needs to use SSL" people would include these points as well.