My family has one and from my experiences it is the best type of mixer on the market. Want to knead dough for a while, or watch TV while the mixer does it for you? Extremely powerful and easy to use.
About adding ingredients, Alton Brown has it down perfectly on Good Eats, buy yourself some flexible cutting boards and just form them in a tube and send the ingredients down in.
As for tilt vs. lift, I don't say it really matters, but in my experiences if you work with REALLY tough dough, the tilt model can rock a little bit while kneading because the motor and dough hook won't get stuck and just keep on chugging, even if that means pushing the top of the mixer up. This is hardly a problem, just slighly annoying for a few seconds. I do not know if the lift models have the same problem, but from my observations, I doubt it. Just try to get a bowl with a handle, it's one of those things that you think "Oh, I won't ever really need it" but if you ever use one you realize the ease of use it has.
As for the ice cream attachment, I haven't had any experience with the KitchenAid attachment, but from the pictures I see online it looks like it has all the correct pieces to make good ice cream, a 2 quart capacity, and being it's from KitchenAid, I'd say go for it as long as you're willing to spend about $80.
http://www.amazon.com/exec/obidos/tg...50543?v=glance
If $80 is a little too much, or you don't have need/space for 2 quarts, this model seems to get pretty good reviews pretty much everywhere, and was the one Alton Brown used on Good Eats if memory serves me right.
http://www.epinions.com/Krups_La_Gla...Makers_R358_70