There has been a fair bit of chatter on the bioware forums and as far as I can see, Bioware are saying the major problems were fixed in the final game, but those fixes came too late to make it into the demo. No doubt there will still be bugs (I haven't seen an RPG yet that didn't at least get up to a 1.3 patch within the first six months) but hopefully they're not game breakers. Realistically though, it's not reasonable to expect the same quality of MP as MW3. That game is purpose built for MP and has a lot more money and resources thrown at it to make sure the servers keep up with demand.
But yes, I've noticed the slow loads and frequent timeouts. I suspect it has as much to do with their servers as the game itself. The demo is after all, something of a public beta for the MP. The SP part of the demo was probably just bait.