We have the ikea levsvik (sp?) and I think its great. We got one for my moms house and its fine. I would use a bassinet or something similar (baby chair, hammock, swing, bassinet) when they are VERY little, but ikea is a great low cost alternative for grandparents. I would not use the ikea mattress for a young child b/c they are very soft, but once they are safer (more like 6-8 months) they are great.
Re: IKEA Gulliver v. Graco Sarah
We have the Gulliver (as do a number of friends) and we all love it.
We got a different mattress though.