I've done several batches of BIAB over the past few years but none for quite a while - mostly because I was cramped for space while renovating the garage and the full system needed to be packed away.
The killer dislike for me was the lack of efficiency. At first I kept coming up way short on my pre-boil gravity despite the BIAB people saying they got better efficiency. Yes, I just upped the grain bill to hit the pre boil gravity but why spend the extra money when you don't need to? The difference in the grain bill price would have been about $5 or so and, after a while, that would pay for the mash tun.
So essentially I think that it's good to use this to go to all grain but it's only a baby step - you still will want to get to a mash tun in the long run to get more stable mash temps, the ability to do larger batches, maximum efficiency (I know as home brewers we shouldn't worry about efficiency but $10 is better in my wallet than anyone else's).
However if it's BIAB or extract, then go BIAB.