I've got a Frog form my now 3 year old DS. I'm oing to be getting it out again in about 7 months time I'm a bit upset you can't get all the lovely new colours as replacement fabric but I refuse to buy another pram when this one cost so much money! The suspension on the front wheels isnt great but not a problem really. Going down a curb can sometimes be tricky but if you go down on the back wheels (iyswim) then it's no trouble.
I also had a sling but DS was a whopper at birth (9.12) so was only in it for a week before my back gave up! Definitely snap up the Frog
can't comment on the frog but those sort of very commercial slings tend to have a really short life, they are not well designed, wrap slings (Kari Me, ellaroo etc...) or soft sings like the ergo have a much longer life and are much more comfortable.
Frog is a fantastic pushchair if it's a good deal snap it up. It has the same wheels as the gecko but the carrycot and seat unit are oth bigger than the gecko one and it has the foam fits on the handles and bumper bar.
Used my frog for last three years with DS and will be getting a buggy board for it in Feb when DC2 arrives. Wouldn't be without it. It is a pleasure to push!
I wouldn't recommend either of the carriers you have mentioned. This type of carrier puts too much pressure on a baby's hip joints and aren't the most comfortable for the parent either. I think they sell because parents are daunted by other choices and at first glance some slings and carriers look quite complicated to put on. But they really aren't and are much better designed. I loved my Wilkinet and carried DS in it until he was almost 12 months (and I'm only 5'2" and 7.5 stones!) and Ergo is also a good one.
Have a look at the Slingmeet website. It gives advice on how to choose and details of local meetings where you can actually try slings.