That'll depend on the price. The GT540m wasn't exactly a great mobile GPU and it added cost to the overall platform. If AMD lingers behind Intel in CPU performance by 10-15% but costs less and delivers better GPU performance and has great battery life then I'd much rather buy a Trinity laptop. If people are buying lappies with low end discrete cards for gaming then they'd probably be better off with Trinity considering you'd get better gaming performance for cheaper.
The four things I want to see with Trinity are
1 admirable CPU performance, roughly on par with an i3 SB. I really don't need any more power than that.
2 a great on-die GPU that trumps the HD4000 and the Llano.
3 Battery life exceeding 6 hours for web browsing.
4 A competitive price for a quality laptop with an optional 1080p screen. I don't care if it can't game at 1080p with 30+ FPS on BF3; I don't expect it to. I just want the option of replacing my desktop entirely
So far the first seems to be true. Even if they're a bit behind that would still suit me quite fine. The second one is almost certainly true and one that I don't think anyone ever doubted or still doubts: AMD can do on-die GPUs and GPUs in general. The latter two won't be answered until we see what the OEMs have for us and how much they feel it's worth. I know AMD initially planned to undercut Intel in the ultrabook space but by how much and whether the OEMs will play ball is another matter entirely.
Make that a CPU performance difference of 50% or more. CPU performance will be lower than a mobile Core i3.
Battery life depends on the capacity of the battery and on power usage of the laptop. Mobile Llano is quite good in this area, on par with Mobile Sandy Bridge. This shouldn't change with Trinity.
Gaming performance won't be anywhere near enough for BF3 at Medium settings at 30FPS. Not even close. AMD won't restrict manufacturers as to what resolution the screens featuring Trinity need to have as that would increase manufacturing costs. That translates to a higher cost to consumers, negating your want for lower costs. Also, good luck replacing a desktop with an APU, unless you want a slow CPU and an okay-ish IGP.
Here's AMD's main problem: most people don't care about gaming on their laptops. At all. Here's their second problem: Intel has better brand recognition. And their third problem: Intel has been very competitive when it comes to pricing lately.
Again, right now you can get a laptop with a Core i5 + GT540M for $600-650. You can get an A8 laptop for $100 less. For that $100, you lose a ludicrous amount of CPU performance and a decent amount of GPU performance. Speaking of which, it's funny you say the GT540M isn't that great when Trinity's IGP should be comparable in performance to it, if not slower.
You're expecting AMD to pull a rabbit out of a hat, and they can't because this is the real world and there's only so much you can do to improve a horrible CPU architecture and a mediocre IGP on the same process node. For the very few that want to do some gaming on the go, the HD 4000 can still play relatively graphically demanding games like DiRT 3 on Medium.