Fred, I feel your pain.
It took almost 20min to download a 14MB file and an hour and a half to download OpenOffice (160MB @ 30KB/s) this morning. iTunes Store downloads are not going any faster, whereas a week ago they were coming down at ~10Mb/s and more. We're also seeing shaping in effect, with downloads coming down at normal at the start, then being locked down as packets are dropped to slow the speeds.
In the last week or so our internet connection has reverted to the state it was in during the darkest days a couple of months back. We've only used a few GB of data this month, and have over 40GB left, so it's not due to hitting our data cap so it is frustrating to say the least. Slingshot keep reiterating they don't shape traffic in any way - however this is not true, and anyone who has working networking knowledge can see the very obvious indicators

Whilst there has been plenty said about this in Slingshot's own forums, amongst others, there has been no response, official or otherwise, as of yet.
Since the Networks team at Slingshot have dragged performance back up before, I'd like to see them do the same again; hopefully in a much shorter timeframe this time around. We're willing to adopt a wait-and-see approach for a short period, to see if/how this is resolved before we look at alternatives.