I would keep the swing. Mamaroo is only for small babies, my dd liked the swing for much longer. You can get a travel swing that folds for smaller option.
No advice, but I'm interested in hearing how long babies can use Mamaroo. I've heard 3 months max from friends who had it before. I'm not sure if I want to get it now, my LO is 3 weeks and we haven't really felt the need for a swing yet. Don't want to spend $200+ (you have to get an infant insert which is $30) for 2 months of use.
DD is 11 weeks and nearly 15lbs (big baby) and does great in the mamaroo. I frequently put her in there for day naps and even when she's awake she's content hanging out or looking at the mobile. It's lightweight, easily moved into other rooms, and plugs into the wall so you don't need to burn batteries. Like CFox said, if possible use a coupon, or even check Craig's list (the cover is machine washable so you don't need to worry about coodies)
I have the mamaroo and I think it's great. The only complaint I have is that the little mobile thing on it isn't motorized so we have to hit it to make it move and entertain my 8 week old. I feel like for $250 it should have a motarized mobile but that's just my opinion!
My son hates it. He will tolerate it while it's off for about 5 mins because he likes to look at the balls that hang above. I agree with pp though; for the amount I spent the mobile balls above should be motorized.
I have heard a few good things about the Mamaroo, but overall, I have come to the conclusion that most people think it is overpriced and their babies like other swings much better. I always check out www.weespring.com- there are really great reviews for products like this. Good luck!
We also received it as a gift and both of ours (twins) love it. I do feel like it took a month or so for them to be big enough to fit in it and not slip down or slump over, which is quite a long time for such an expensive product since it's only in use for a limited time. It doesn't cradle them as much as our snug-a-bunny swing or RnP does. And I agree that for $200+ the mobile should at least spin. That being said, they both do really love it now that they fit better in it. They both take turns sleeping in it and I can see using it quite a bit for the next few months. It has a built in sound spa too, which is nice.
We like our Mamaroo but it isn't a must-have. I use it to be able to brush my teeth and put contacts in- my little one gets bored pretty fast. It's frustrating too that they put a mobile on it but it doesn't spin! That would make it a lot more fun for baby.
Re: Mamaroo
It's a great baby sitter for us.
I agree with the baby sitter comment. Lol