Does seem to make the feature
almost pointless I guess. The benefit of iMessage is all your messages everywhere so you can follow a conversation across devices. Hopefully it's something they'll look at soon.
Edit: so, while at work, the first time I opened iMessage on the iPad i got the prompt asking if want to use my phone to relay SMS. Obviously chose yes. Was not expecting this would work away from home wifi - I have no idea why I wasn't - but I was pleasantly surprised when an SMS came in and it appeared on the iPad, all over cellular. Nice.
Now, question: I left home before enabling the functionality on my iMac but once enabled will these SMS come through to my Mac when I'm away since it seems it's just using iCloud to sync these, or is there still a Bluetooth proximity requirement for it to work?