Given the rate that GPH releases handhelds, it might not be a few years. Of course, if screen real estate is paramount to you, you could go with one of those Chinese tablets - emulation on Android is decent with enough horsepower under the hood (re: in the 150-250USD range), but then you lose the dedicated controls and have to rely on onscreen ones, which lack that tactile goodness of button mashing.
And there's nothing wrong with the Pandora as a device, in my opinion - you get what you pay for, which amounts to a pocket computer. I don't have a particular need for a pocket computer, thus I went with a Caanoo.
As far as your question - I haven't tried the games you mentioned, but mouse emulation in the few games I've tried is pretty decent, just takes a bit of getting used to, since it's not entirely intuitive the first time. The touchscreen doesn't seem to calibrate well (or, maybe it's just me) with Uae4All, nor does a screen tap translate to a click, so you'll end up "dragging" the cursor around with the stylus or your finger, then use one of the buttons to click. I know that that may sound tedious, but trust me, it really isn't, and after a minute, you won't even notice.
Of course, you can also use the analog nub to move the cursor around as well, but I figure, hey, it's got a touchscreen, might as well use it.
Outcast, the AtariST emulator, doesn't have touchscreen support at all yet, so you'll have to rely on the nub. Generally, while I grew up with an ST and have much love for it, I found that Uae4All is better, probably due to the fact that it's been under development longer.
