This is the upload speed I use with my slingbox and it is more than acceptable - but it aint full screen. 

Sport is the real killer of compression and I am able to watch cricket/football without to much concern.

IF you expect perfection then you will get disappointed - if you are after something that is watchable and assume any picture is better than none then you will be pleasantly surprised. :-)

 I don't remember many people posting  (if any?)that they are returning there slingbox because of remote streaming quality...

Only UK Based Moderator on Sling Community....Please don't PM me technical questions.

I run about 450k on my laptop remotely with no problem.  I have a 768k upload pipe but I reserve some of my bandwidth for other purposes.  Anything above 250K is very acceptable - even in full screen on my 17" MacBookPro.  I would say that at 350K, you should do fine.  Again, not perfect, but plenty good for watching re-runs of Law and Order or CSI! :)

Slinging with a SlingCatcher, a ProHD, a Pro, a Solo, an AV, and a Slingbox Classic. 3 Replay TV units, a Roku Photobridge and a Roku M2000 Soundbridge, an AppleTV, a Vudu, and digital cable. www.na9d.net